The concept of entrustment has garnered significant attention in medical specialties, despite variability in supervision styles and entrustment decisions. There is a need to further study the enactment of supervision on inpatient wards to inform competency-based assessment design. Attending physicians, while supervising on clinical teaching inpatient wards, were invited to describe a recent moment of enacting supervision with an internal medicine resident. Constructivist grounded theory guided data collection and analysis. Interview transcripts were analysed in iterative cycles to inform data collection. Constant comparison was used to build a theory of supervision from the identified themes. In 2016-2017, 23 supervisors from two Canadian universities with supervision reputations ranging from very involved to less involved participated in one or two interviews (total: 28). Supervisors were not easily dichotomised into styles based on behaviour because all used similar oversight strategies. Supervisors described adjusting between 'hands-on' (e.g. detail oriented) and 'hands-off' (e.g. less visible on ward) styles depending on the context. All also contended with the competing roles of clinical teacher and care provider. Supervisors made a distinction between the terms `entrust' and `trust', and did not grant complete entrustment to senior residents. We propose that a supervisor's perceived responsibility for the ward underlies adjustments between 'hands-on' (i.e. personal ward responsibility) and 'hands-off' (i.e. shared ward responsibility) styles. Our approaches to clinical supervision model combines this responsibility tension with the tension between patient care and teaching to illustrate four supervisory approaches, each with unique priorities influencing entrustment. Given the fluidity in supervision, documenting changes in oversight strategies, rather than absolute levels of entrustment, may be more informative for assessment purposes. Research is needed to determine if there is sufficient association between the supervision provided, the entrustment decision made and the supervisor's trust in a trainee to use these as proxies in assessing a trainee's competence.