Leave work in the course of strike (3,2)
I believe the answer is:
hop it
'leave' is the definition.
(I've seen this before)
'work in the course of strike' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'in the course of' is an insertion indicator.
'strike' becomes 'hit' ('hit' can be a synonym of 'strike').
'op' placed into 'hit' is 'HOP IT'.
(Other definitions for hop it that I've seen before include "On your bike!" , "shove off" , "Go away (colloq.)" , "Run along now!" , "Scram!" .)