RELATIONSHIP BETWEEN LEADERSHIP OSTRACISM AND EMPLOYEE ENGAGEMENT: A MODERATED MEDIATION MODEL

This study investigated the effect of leadership ostracism on employee engagement through defensive silence as a mediating variable, using the conservation of resources theory framework and the need-threat/need fortification model. The study also examined the role of external social support, which has the potential to moderate the indirect effect of leadership ostracism on employee engagement. Data were collected from civil servants in Indonesia using self-report questionnaires. Using the snowball sampling technique, an online survey was conducted to collect data. Of 504 accepted responses, 310 met all the criteria and were analysed using partial least square-structural equation modelling (PLS-SEM) and a moderated mediation model. The moderated mediation analysis showed that low perceived external social support indirectly strengthens the negative influence of leadership ostracism on employee engagement through defensive silence. This research enriches the ostracism literature, especially regarding leadership ostracism and its relationship with employee engagement, which has not been empirically tested in previous studies.


INTRODUCTION
Employee engagement is essential to today's business sustainability and success (Stein et al., 2021).Previous research suggests that employees with higher engagement levels tend to have more positive emotional states (Bakker et al., 2014), high work performance, and better physical and psychological well-being (Bakker et al., 2008).Thus, employee engagement remains a challenge for managers, as featured in Gallup's State of the Global Workplace 2021 Report, which indicated that global employee engagement decreased from 22% in 2019 to 20% in 2020, including for Indonesia (Gallup, 2021).Therefore, further research is needed to better understand the antecedents of employee engagement.
Despite efforts to improve employee engagement, ostracising individuals in the workplace has become more prevalent (Scott et al., 2015;Williams, 2001;Williams & Sommer, 1997).Workplace ostracism (i.e., feeling ignored or unworthy) significantly influences employees and the organisation (Ferris et al., 2008); regardless of the underlying motives of ostracism, feeling ignored is a painful experience.Ostracism has additional detrimental effects, such as anti-performance behaviour (Duffy et al., 2002), high employee turnover (O'Reilly et al., 2015), and decreased organisational citizenship behaviour (Ferris et al., 2008).But most of the research done before (Ferris et al., 2008) only looked at the target or victim, not the source of the ostracism, which could have a different effect on employee outcomes (Hitlan et al., 2006).According to the source, workplace ostracism can be looked at both from a horizontal (co-workers) and a vertical (leaders) point of view.In fact, leadership ostracism has more negative effects than other kinds on ostracism (Zhao et al., 2019).
In a leadership process involving interactions between leaders and subordinates, employees are often ostracised by their leaders, such as being denied significant roles at work (Williams, 2007;Zhao et al., 2019).As mentioned earlier, regardless of motive, ostracism imposes negative consequences on an individual, especially ostracism enacted by their leader.While previous studies have examined ostracism and its effects on employees and organisations, there is little empirical evidence on how employees feel ostracised by their employers and their responses to ostracism (Chang et al., 2019).Subsequently, scholars have encouraged research on leadership ostracism to further understand how ostracism affects employees, organisations, and labour relations (Wu et al., 2015;Zhao et al., 2019).
Previous studies conducted by Xu et al. (2020) have explored the effect of workplace ostracism on employee engagement and found that being ignored or excluded by others at work causes disengagement.However, that study does not specifically consider the source of ostracism itself.There is no research that specifically examines the effect of leadership ostracism on employee engagement.Accordingly, this study examined the effects of leadership ostracism on employee engagement.Since employee behaviour is a complex interaction of individual, situational, organisational, and macro-cultural factors (Tan et al., 2021), this study also explored the mechanism through which leadership ostracism decreases employee engagement.According to the need-threat-fortification framework developed by Williams (1997), ostracism experienced by employees involving coworkers and employers is likely to threaten self-efficacy, control, and meaningful existence regarding self-esteem and belongingness.The framework also explains that if employees' psychological and behavioural needs are not met, this condition will risk their psychological well-being.In line with findings from research conducted by Jahanzeb et al. (2018), leadership ostracism can threaten efficacy needs, such as power and meaningful existence.They asserted that ostracised employees use defensive silence as a coping mechanism to maintain social harmony, avoid conflicts, and help restore their need for control, power, and a meaningful existence.Unfortunately, defensive silence has been found to induce several adverse effects such as stress, dissatisfaction, and cynicism (Morrison & Milliken, 2000), lead to increased emotional exhaustion (Jahanzeb et al., 2018), hamper creativity (Chenji & Sode, 2019), and reduce employee engagement (Wang et al., 2020a).Therefore, using the need-threat-fortification framework, this study examined the effects of leadership ostracism on employee engagement, with defensive silence as a mechanism that mediates the relationship between the two constructs.
Moreover, to further explore these constructs, we strove to identify the key boundary condition of the causal sequence.Based on the conservation of resources (COR) theory, people who lack resources are predicted to adopt a defensive silence in order to guard their resources.Accordingly, we were interested in understanding how the decision to be defensive silence, which mediates the effect of leadership ostracism on work engagement, is different for individuals who differ in resource availability.Social support is one significant resource for individuals to encounter stress, in which individuals with high social support perceive a stressor to be less stressful than those with low social support (Pilcher et al., 2016).We focused on external social support since work relationships are closer to the ostracism source and often have conflicting motives, interests, or relationships with the ostraciser.Bonds forged outside of work may be better suited to shoring up the threatened needs associated with workplace ostracism (Fiset et al., 2017).We predict that individuals who do not have much social support from the outside will tend to shut up as a way of protecting themselves when they are being ostracised by the leader, which in turn leads to work disengagement.Drawing on these insights, this study proposed that external social support can function as a boundary condition for the indirect effect of leadership ostracism on employee engagement.
This study makes a significant contribution to this topic.First, it expands the literature on leadership ostracism and its relationship with employee engagement, which previous studies have not empirically investigated.Under the COR theory (Hobfoll, 1989) and the need-threat/need fortification model (Williams, 1997) framework, we examined the relationship between leadership ostracism and employee engagement both directly and indirectly.Second, this study conducted a moderated mediation analysis to investigate the role of external support on the indirect effect of leadership ostracism on employee engagement through defensive silence.According to Williams (2009), it is necessary to further examine the possible buffering mechanisms that can moderate the negative effects of ostracism experienced by individual workers.In the last 20 years, several studies have demonstrated the moderating effects of employees' perceived external support on the relationship between various job stressors and both work and life outcomes (Fiset et al., 2017).Thus, in addition to providing evidence that leadership ostracism negatively impacts employee engagement, this study also identified a leverage point that can potentially reduce the negative effects of ostracism, especially ostracism by leaders.

Conservation of Resources Theory
The COR theory refers to the stress theory which was developed by Hobfoll in 1989.This theory has a fundamental principle that is individuals will attempt to maintain, protect, and pooling resources.The resources in this regard comprise objects which fulfill objectives (such as food, clothing, and shelter), personal characteristics (such as self-esteem, knowledge, or skills), social support, conditions (perceived acceptance and support from the people in the surroundings, job security, good marriage), and energy (money, knowledge, and time).Many individuals consider these resources as objects which function as instruments to achieve meaningful attainment or valuable possession (Hobfoll, 1989).Within the context of an organisation, these resources include physical, emotional, and cognitive assets such as support from supervisors or co-workers, trust in the organisation, selfefficacy, and feedback on job performance (Bakker & Demerouti, 2007).The resources are used by employees to attain goals and cope with work-related stress that they experience (Bedi, 2019).Therefore, the COR theory proposes that stress is created when individuals feel threatened by the loss of resources, actually lose resources, or being unable to provide resources.On the contrary, individuals with unrestricted access to resources that are perceived as valuable tend to display better states of readiness for coping with work demands (Wright & Hobfoll, 2004).In this study, the COR theory will serve as the basis for explaining how leader ostracism affects employee engagement.

Need-Threat/Need Fortification Model
The need-threat/need fortification model is widely known as a framework explaining that ostracism is a threat that erodes the targets' personal resources.Developed by William (1997), this framework integrates the need theory and COR theory.Specifically, this model describes ostracism as a threat to humans' four basic needs, namely need to belong, need for self-esteem, need for control, and need for a meaningful existence.As proposed in the COR theory, individuals will protect and fortify the needs at risk using all possible manners (Hobfoll, 1989;Scott & Duffy, 2015;Williams, 2007).As an example, based on previous findings, individuals who perceive that their need to belong and need for self-esteem are under threat may be involved in pro-social behaviours to win sympathy or build positive relationships with others (Williams & Sommer, 1997).However, when ostracism is perceived as threatening the need for control and the need for a meaningful existence, targets may respond with anti-social behaviours (such as aggression and enmity).Leadership ostracism is known to threaten employees' need for control and their need for a meaningful existence (Jahanzeb et al., 2018).The need-threat/need fortification model will serve as a basis for explaining the effects of leadership ostracism on employee self-defense mechanisms, specifically defensive silence, and its effect on employee engagement.

Leadership Ostracism and Employee Engagement
Employee engagement is the degree of psychological presence when employees perform organisational roles (Saks, 2006).Schaufeli et al. (2002) defined employee engagement as a positive, fulfilling work-related state of mind characterised by vigour, dedication, and absorption.Vigour concerns employees' psychological state, as indicated by feelings of happiness and willingness to work, which are often reflected in energy, perseverance, and determination in coping with problems.Dedication relates to a strong bond to the job performed, as characterised by a sense of significance, enthusiasm, inspiration, pride, and challenge.Absorption concerns employees' perception of how quickly time passes when performing duties (Schaufeli et al., 2006).Therefore, employee engagement is crucial to the organisation because employees' work performance is a direct function of their engagement (Haldorai et al., 2020).
In the context of workplace relationships, there are occasions when leaders ignore and ostracise employees, hinder employee promotion, and deprive employees of training opportunities, to prevent their success (Xue et al., 2020).Therefore, when employees feel ostracised by their leaders, their workplace attitudes and behaviours are affected by the unavailability of resources, such as information or valuable feedback, opportunities to influence, or the work relationships and operational support necessary to complete tasks and succeed at work.Employees can decrease their level of work engagement by refraining from attitudes or behaviours that contribute to the organisation (Haldorai et al., 2020).Based on COR theory (Hobfoll, 1989), leader ostracism induces employee stress through the threat of losing resources and access needed for career progress.When individuals lack adequate resources to meet work demands, they are more likely to disengage from work, which will impact work outcomes (Leung et al., 2011).For example, individuals who perceive themselves as ostracised by their employers assume that they will not receive their employers' support; consequently, they will lack the main driver of employee engagement (Cheng et al., 2013;Jose & Mampilly, 2015).Thus, based on the COR theory, leader ostracism has the potential to affect employee engagement negatively.This is supported by previous research, which suggests that workplace ostracism decreases employee engagement (Haldorai et al., 2020;Leung et al., 2011).Therefore, this study proposed the following hypothesis: H1: Leadership ostracism has a negative effect on employee engagement.

Leadership Ostracism and Employee Engagement: Mediating Role of Defensive Silence
From the perspective of the need-threat/need fortification model (Williams, 1997), individuals are inclined to maintain, protect, and obtain resources.When they sense that their resources are at risk, they experience chronic stress and use reserve resources to employ active adaptation strategies to prevent further resource loss.Being ostracised in the workplace is a stress-inducing condition that threatens employees and drains their energy and physical and emotional resources (Ferris et al., 2008).The COR theory (Hobfoll, 1989) asserts that employees may adopt conflict avoidance strategies in response to employer ostracism to mitigate the undesirable stress effects and protect their remaining resources.Conflict avoidance is a safe way to practice defensive silence in response to leadership ostracism.Defensive silence is rooted in fear and includes withholding ideas, information, and opinions as a form of self-protection, which is relevant to COR theory.Jahanzeb et al. (2018) found that individuals respond to supervisor ostracism by exhibiting defensive silence to protect themselves from a greater drain of their resources.Accordingly, this study proposed the following hypothesis: H2: Leadership ostracism has a positive effect on defensive silence.
Deciding to be silent out of fear and as an effort to protect themselves makes employees feel that they lack control over their work and feel worthless (Morrison, 2014).This makes them lose internal work motivation (i.e., employee engagement) due to reduced job autonomy as a result of a loss of control over work (Hackman & Oldham, 1976).This statement is supported by previous research which states that employee silence reduces employee engagement (Wang et al., 2020a).Therefore, the following hypothesis is formulated: H3: Defensive silence has a negative effect on employee engagement.
In line with the COR theory's idea that "loss begets loss," defensive silence leads to further losses which manifest as loss of energy and drive to work (Shaukat & Khurshid, 2022).Silence makes individuals disengage from their work (low work engagement) since isolation induced by silence makes their overall work environment worse (Milliken & Morrison, 2003) and undermines their internal work motivation (Morrison, 2014;Wang et al., 2020a).Following this line of reasoning, we argue that employees will respond to leader ostracism by remaining silent at work and then with a reduction in work engagement.That is, employee silence would function as a mediating mechanism underlying the relationship between leader ostracism and employees' work engagement.Thus, this study proposed the following hypothesis: H4: Defensive silence mediates the relationship between leadership ostracism and employee engagement.

The Moderating Role of Perceived External Social Support
The effect of employees' defensive silence on their work engagement level may differ by the extent of their external social support.Social support is a fundamental concept in work stress and well-being research.Previous research demonstrated that higher levels of communal support increase mental well-being and the ability to cope with traumatic events (Lakey & Orehek, 2011).Previous studies also found that employees who received support from family and friends were better able to cope with overall life dissatisfaction regarding job insecurity, physical and psychological stress, and anxiety (Frese, 1999).High external social support (from family and friends) reduces employees' feelings of unworthiness and inability to maintain control over their work, allowing them to better maintain work engagement.Hence, this study proposed the following hypothesis: H5: Perceived external social support moderates the negative relationship between defensive silence and employee engagement.
From the above discussion, we proposed a second-stage moderated mediation hypothesis, as illustrated in Figure 1.Hayes (2013) described second-stage moderated mediation as a model with a moderating effect on the second path of the independent variable's indirect effect on the dependent variable via the mediator.
According to the COR theory, individuals who are lacking resources (e.g., a poor relationship with their supervisor) may adopt a defensive silence in order to protect their remaining resources (Ng & Feldman, 2012).However, the decision to be silent may differ between individuals who have high social support and those who have low social support.According to the perspective of the stress-buffer model, those who have limited social supports are affected more negatively than those who have high social support when they are exposed to stress (Cassel, 1976).
In the context of leadership ostracism, external or non-work social support may be more suited to shoring up the threatened needs that are associated with being ostracised by leaders in the workplace (Fiset et al., 2017).We assume that people who do not have a lot of social support outside of the organisation will tend to shut up when the leader ostracises them as a way to protect themselves.This, in turn, will make them less willing to engage in their work.Therefore, we proposed the following hypothesis: H6: Leadership ostracism influences employee engagement through its relationship with defensive silence, and the indirect effect will be stronger under low levels of perceived external support than under high levels of perceived external support.

Sample and Procedures
The study population included civil servants who worked at various Indonesian government institutions.We focused on individual participants and used a selfreport questionnaire to assess their perceived leadership ostracism, defensive silence, employee engagement, and perceived external social support.First, using a snowball sampling technique, a link to an online survey was sent to public officials who were asked to participate and to share the link with other civil servants in their employment areas.Second, the researchers recruited key persons to assist in data collection and sent the online questionnaire to other respondents.The online questionnaire was distributed to each key person in the institution via email.
To determine the minimum sample size estimation, we used the inverse square root method.In this study, we expected the minimum path coefficient to be significant between 0.11 and 0.20. .About 51% of the respondents held a bachelor's degree, 22.58% held a master's degree, 0.97% held a doctoral degree, 12.48% held an associate degree, and 13.23% held a high school diploma.About 8% of respondents had less than one year of service, 11.61% had 1-3 years, 5.48% had 4-5 years, and 74.84% had more than six years of service.

Measures
Perceived leadership ostracism was measured using the 5-item scale developed by Hitlan and Noel (2009) to determine the extent to which an individual perceived ostracism or was avoided by their supervisor; for example, "Leaders not replying to your requests/questions within a reasonable period."Defensive silence was measured using a 5-item scale developed by Van Dyne et al. (2003), which measures how an individual withholds ideas, information, or opinions to protect themselves from fear; for example, "I do not speak up and suggest ideas for change, because of fear."Employee engagement was measured using a 9-item scale adopted from Saks (2006) to examine the degree to which individuals are engaged in their work; for example, "I really 'throw' myself into my job."Perceived external social support was measured using a 6-item scale adopted from Spreitzer (1995) to determine the degree of support an employee received outside work; for example, "People outside of my workplace really count on listening to me when I need to talk."The items of each measure were assessed on a 5-point Likert scale (1 = "strongly disagree" to 5 = "strongly agree").

Analysis Strategy
Partial least squares-structural equation modelling (PLS-SEM) was used to test the proposed hypotheses using SmartPLS 3.3.3.Due to the limited availability of prior knowledge on structural model relationships or the theory is less developed, PLS-SEM was considered more appropriate, especially if the primary goal is to explain target constructs (Hair et al., 2017).To test the second-stage moderated mediation hypothesis, we employed the process macro (Model 14) produced by Hayes (2013) using the Statistical Package for the Social Sciences (SPSS) 26.0.

Preliminary Analysis
Table 1 illustrates the variable means, standard deviations, and correlations.The correlations were consistent with the initial assumptions.Leader ostracism was positively correlated with defensive silence (r = 0.41, p < 0.001) and negatively correlated with employee engagement (r = -0.40,p < 0.001) and perceived external social support (r = -0.23,p < 0.001).Defensive silence was also negatively correlated with employee engagement (r = -0.33,p < 0.001) and perceived external social support (r = -0.21,p < 0.001).Employee engagement was positively correlated with perceived external social support (r = 0.47, p < 0.001).

Reliability and Validity Assessment
To assess reliability, the composite reliability value was calculated and used as an assessment criterion, where a composite reliability value larger than 0.7 indicates that the construct has acceptable internal consistency reliability.As illustrated in Table 2, the composite reliability for each construct was greater than 0.7, indicating good reliability.
Convergent and discriminant validity were evaluated to ascertain validity.A construct fulfils the convergent validity requirement if the indicator's outer loading is greater than 0.70 or the value of the average variance extracted (AVE) is higher than 0.50.To assess discriminant validity, we used heterotrait-monotrait (HTMT) criteria with a 0.90 threshold (Hair et al., 2017).As illustrated in Table 2, after eliminating several items' factor loading values less than 0.7, the factor loading value of each indicator was greater than 0.7.Additionally, analysis results demonstrated that all constructs' AVE values were above 0.5, indicating that the convergent validity requirement was satisfied.Table 3 illustrates the HTMT 0.90 values for each construct, with all construct values less than 0.90, meeting the discriminant validity requirements.The analysis results illustrated in Tables 2 and  3 provide the basis for the next testing stage, with validity and reliability criteria met.

Hypotheses Testing
H1 to H4 testing was conducted using PLS-SEM through a bootstrapping process with 1,000 resamples (Hair et al., 2017).Before testing the hypotheses, a full collinearity assessment (Kock, 2015) was conducted to investigate whether common method bias (CMB) affects our proposed model.The model can be considered free of CMB if the variance inflation factor (VIF) values are equal to or lower than 3.3 (Kock, 2015).Our findings showed that the values ranged from 1.066 to 1.326 (Table 4), which indicates that there is no CMB.As illustrated in Table 5, leadership ostracism significantly negatively affected employee engagement (ß = -0.266,p < 0.001), supporting H1.The analysis also demonstrated that leadership ostracism significantly affected defensive silence (ß = 0.417, p < 0.001).Defensive silence significantly negatively affected employee engagement (ß = -0.151,p = 0.012), supporting H2 and H3.Leadership ostracism indirectly affected employee engagement via defensive silence (ß = -0.063,p = 0.018), supporting H4.Since the results indicated that leadership ostracism also directly affects employee engagement, defensive silence fully mediates the relationship between leadership ostracism and employee engagement.To test the moderating effect of perceived external social support, the researchers adopted Hayes' ( 2013) method for second-stage moderated mediation.Table 5 illustrates that perceived external social support moderated the negative relationship between defensive silence and employee engagement (ß = 0.154, p = 0.007), supporting H5.To determine the nature of the moderating effect, we adopted Aiken and West's (1991) procedure to plot the interaction.Consistent with H5, Figure 2 illustrates that defensive silence had a stronger negative relationship with employee engagement when perceived external social support was low.
H6 predicted that the mediated relationships would be weaker when perceived external social support was high, meaning that the conditional indirect effect of leader ostracism on employee engagement through perceived external social support would be weaker when an individual perceived high external social support.Based on the moderated mediation analysis, Table 6 illustrates that the conditional indirect effect of leadership ostracism on employee engagement was significant when perceived external social support was low (ß = -0.10,boot SE = 0.04, 95% bias-corrected CI = [-0.17,-0.02]) but not significant when perceived external social support was high (ß = -0.02,boot SE = 0.03, 95% bias-corrected CI = [-0.08,0.04]), supporting H6.

DISCUSSION
In a view of the evidence for the detrimental effect of workplace ostracism, there is no research that specifically examines the effect of leadership ostracism on employee engagement including the boundary conditions and mechanism by which this relationship occurs.Using COR theory and the need-threat/need fortification framework, this study investigated the effect of leadership ostracism on employee engagement using moderated mediation analysis.We examined how leader ostracism is related to employee engagement through defensive silence.
We also clarified the role of perceived external social support as a moderating variable.
This research found that leadership ostracism has a significant negative effect on employee engagement, either directly or indirectly.First, being ostracised by leaders is proven to directly reduce employees' levels of engagement.This finding aligns with COR theory, exposure to leadership ostracism depletes the resources needed to motivate individuals (Hobfoll, 1989).Leader ostracism potentially depletes task resources (Kwan et al., 2018) that employees need to solve problems, accomplish their work, and advance their careers.Ostracised individuals tend to respond to such threats by preserving the remaining valuable resources through reduced work engagement (Leung et al., 2011).Second, leadership ostracism decreases employee engagement via defensive silence.The result of this study suggests that when employees feel like their leader is ostracising them, they are more likely to keep information or opinions about work-related issues to themselves.This, in turn, makes them less engaged in their jobs.
The result of this study shows the positive influence of leadership ostracism on defensive silence.It aligns with the need-threat/need fortification model (Williams, 1997), which says that employees use defensive silence as a way to deal with threats related to being ostracised by the leader, which could drain their personal resources.Therefore, employees who have been ostracised are likely to withhold information or opinions regarding work-related issues to protect their remaining resources and avert further losses.Accordingly, this study reaffirmed leadership ostracism as a potential predictor of defensive silence, as stated earlier by Jahanzeb et al. (2018).In the face of perceived leadership ostracism, adopting defensive silence is considered a reasonable and immediate behavioural response.
Our finding also confirms the detrimental effect of defensive silence on employee negative attitudes.The negative effect of defensive silence on employee engagement supports the prior proposition from Morrison (2014) in which defensive silence negatively impacts employees' intrinsic motivation.Prior findings have also demonstrated that employee silence results in lower levels of employee engagement (Wang et al., 2020a).Defensive silence has a negative effect on individuals because they are reluctant to contribute their ideas, information, and opinions to the organisation.Employees feel unworthy because of their silence, which may lower their sense of autonomy because they cannot control their work.This lack of control induces negative consequences, such as intrinsic motivation (Hackman & Oldham, 1976), which in turn decreases employee engagement.
The findings demonstrate that perceived external social support moderates the relationship between defensive silence and employee engagement.Employees' reluctance to convey their ideas, opinions, or information leads to stronger disengagement when external social support (family or friend) is low.Additionally, perceived external social support moderates the indirect relationship between leader ostracism and employee engagement through defensive silence.The moderated mediation analysis demonstrated that employees use defensive silence as a way to respond to being left out by leaders when they do not have a lot of social support from the outside, which makes them less engaged.Our findings suggest that a low level of external social support makes it more difficult for individuals to deal with leader ostracism because they lack a supportive social circle that can restore their self-efficacy and sense of self-worth.This leads employees to engage in defensive silence, which decreases their motivation to demonstrate vigour, dedication, and absorption in their work.Studies have demonstrated that social support reduces the negative impact of social stressors at work (Viswesvaran et al., 1999), including ostracism.Social networks allow individuals to recognise their self-worth, control, and expertise (Zhang et al., 2020).Previous findings have also demonstrated that ostracised individuals tend to activate their social selves by looking for real social interactions or thinking about friends or family to minimise the detrimental effects of workplace ostracism (Uskul & Over, 2017).

Theoretical Implications
This study has two essential theoretical implications.First, most previous research on workplace ostracism has focused on the target/victim, regardless of the source of ostracism.Of course, ostracism by leaders and ostracism by co-workers will have different effects on victims.Few studies have explored the disparate effects of leader and co-worker ostracism on employees' work-related behaviours (Jahanzeb et al., 2018).In order to understand the impact of workplace ostracism on employee engagement, most previous studies have generally not looked specifically at the source of ostracism.For example, prior research found that workplace ostracism has a detrimental effect on work engagement (Haldorai et al., 2020;Leung et al., 2011) but does not specifically address other sources of social exclusion, such as leader ostracism, which triggers differentiated psychological processes and potentially produces different outcomes (Hitlan & Noel, 2009).The current study makes a novel contribution by specifically focusing on exploring the influence of leadership ostracism on employee engagement, which has not been examined by previous studies.This study is the first to show that leadership ostracism has a detrimental impact on employee engagement.
Second, this study not only looks at the direct effect of leadership ostracism on employee engagement, but it also includes mediating and moderating variables to get a full picture of this relationship.Using COR theory and the need-threat/need fortification framework, empirical evidence was obtained for the mediating role of defensive silence in the relationship between leadership ostracism and employee engagement.Rather than focusing on task-related motivation, this research centres on self-protective mechanisms ostracised employees may adopt to protect their remaining resources.Also, this study answers the call for research that examines the possible buffering mechanisms that moderate the negative effects of ostracism experienced by individual workers (Williams, 2009).This study fills the gap by examining whether, how, and when defensive silence as a coping strategy relates to leadership ostracism and employee engagement by looking at the perceived external social support from a target perspective.There is no previous research on a moderated mediation process that shows how leadership ostracism and employee engagement are related.Therefore, by using moderated mediation analysis, this study offers a new avenue to understanding how leadership ostracism affects employee outcomes.

Practical Implications
The findings offer a guide for practitioners to better understand how leadership ostracism relates to employee engagement.First, it confirms the negative effects of leader ostracism on employee engagement, suggesting that organisations aiming to enhance employee engagement should employ actions that discourage leadership ostracism.Organisations could facilitate specific leader or supervisor training programmes to increase leaders' understanding and skill to detect whether their intentional or unintentional behaviour makes employees feel ostracised.For example, role-plays could facilitate practising and developing leaders' interpersonal skills, including communication, active listening, giving and receiving feedback, conflict management, team building, and negotiation.
Second, the findings on the detrimental impact of defensive silence on employee engagement also imply that lowering employees' defensive silence can boost employee engagement at work, indicating the need to provide an environment in which employees may voice their concerns and thoughts about work-related issues in their company (Morrison, 2014).Organisations could reduce employee silence by developing a caring work atmosphere, offering employees the opportunity to voice their problems, and listening to their voices through communication and involvement, which could enhance employee engagement at work.
Third, the finding show that ostracised individuals who perceived low external social support tend to be silent in order to protect their remaining resources, thereby reduce their work engagement.Responding to the research findings, we suggest organisations provide facilities in an effort to increase non-work social support, such as providing support for employees to have membership in a club or external community based on a particular hobby or interest.For example, businesses can form business-to-business (B2B) partnerships with gyms or golf clubs to give their employees access to communities outside of work and boost their sense of social support outside of work.

Limitations and Suggestions for Future Research
This study has some limitations.First, it used data from civil servants from a range of Indonesian government institutions, the culture or characteristics of which differ from those in other sectors or areas.Accordingly, caution should be exercised when generalising the findings to other populations.Second, the cross-sectional design applied in this study prevented a more in-depth analysis of the leadership ostracism phenomenon, defensive silence, employee engagement, and perceived external social support because the data pertained to a single period.Third, the data were limited to the participants' responses to the questionnaire items.Richer information would be obtained from in-depth interviews.
However, this study opens an interesting avenue for future research on leadership ostracism.First, future research should consider other mediating variables, such as organisational cynicism as a mediating mechanism linking leader ostracism to employee engagement.Cynicism toward an organisation can arise when employees are confronted with job-related stress (Andersson, 1996).Second, in response to Williams (2009), it is necessary to further examine the possible buffering mechanisms, such as emotional intelligence, that may moderate the negative effects of ostracism experienced by individual workers.Third, future studies should involve more participants from other sectors, such as healthcare organisations (e.g., hospitals), to capture a better understanding of workplace ostracism.

CONCLUSION
Using COR theory and the need-threat/need fortification framework, this study analysed the effect of leadership ostracism on employee engagement using moderated mediation analysis.The findings indicate that leadership ostracism negatively affects employee engagement directly and indirectly via defensive silence.The moderated mediation analysis showed that a low level of perceived external social support indirectly increases the negative effect of leadership ostracism on employee engagement through defensive silence.

Figure 2 .
Figure 2. Perceived external social support's moderating effect on the relationship between defensive silence and employee engagement

Table 1
Mean, standard deviation, and zero-order correlations

Table 2
Assessment result for the measurement model

Table 4
Results of the full collinearity assessment

Table 5
Summary of results

Table 6
Second-stage moderated mediation