Leave -- usual time (4)
I believe the answer is:
part
'leave' is the definition.
(part can mean to leave or depart)
'usual time' is the wordplay.
'usual' becomes 'par' (par is an average golf score).
'time' becomes 't' (abbreviation).
'par'+'t'='PART'
(Other definitions for part that I've seen before include "unemployed actor hopes for" , "Constituent - something to play?" , "Divide; role" , "Portion of a whole" , "Separate - role" .)