Make a choice — work ahead of time (3)
I believe the answer is:
opt
'make a choice' is the definition.
(I've seen this before)
'work ahead of time' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'ahead of time' becomes 't' (I've seen this in other clues).
'op'+'t'='OPT'
(Other definitions for opt that I've seen before include "End or act of shutting" , "Have preference for something" , "Choose from pot" , "Hold in the highest esteem" , "Prefer, choose" .)