Retired thespian ignoring head of casting's staffing schedule (4)
I believe the answer is:
rota
'staffing schedule' is the definition.
(schedule for staff in a place of work)
'retired thespian ignoring head of casting's' is the wordplay.
I cannot quite see how this works, but
'retired' could be 'r' (abbreviation) and 'r' is located in the answer.
'of' could be 'o' and 'o' is present in the answer.
The remaining letters 'ta' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
(Other definitions for rota that I've seen before include "Register of names for duties" , "Duty schedule" , "Duty roster" , "Roll call or roster" , "List assigning turns of duty" .)