After trick is set up, maybe watch worker not doing all the hours (4-5)
I believe the answer is:
part-timer
'worker not doing all the hours' is the definition.
(someone who only works part-time)
'after trick is set up maybe watch' is the wordplay.
'after' is a charade indicator (letters next to each other).
'trick' becomes 'trap' (I've seen this in another clue).
'is set up' shows that the letters should be reversed in order (in a down clue, letters go up).
'maybe watch' becomes 'timer' (a watch might be used to time something).
'trap' in reverse letter order is 'part'.
'part' put next to 'timer' is 'PART-TIMER'.
(Other definitions for part-timer that I've seen before include "worker on reduced hours" , "One not working the whole week" , "One working reduced hours" , "Casual worker" , "One working less than a full week" .)