Doctor has work decrease (4)
I believe the answer is:
drop
'decrease' is the definition.
(I know that drop is a type of decrease)
'doctor has work' is the wordplay.
'doctor' becomes 'dr' (abbreviation).
'has' is a charade indicator (letters next to each other).
'work' becomes 'op' (common abbreviation for 'opus').
'dr'+'op'='DROP'
(Other definitions for drop that I've seen before include "Finish with" , "Shoot" , "Go to ground" , "Sweet; fall" , "lower" .)