Fight doctor in film (6)
I believe the answer is:
combat
'fight' is the definition.
(combating is a kind of fighting)
'doctor in film' is the wordplay.
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'in' is an insertion indicator.
'film' becomes 'coat' (I've seen this in other clues).
'mb' going inside 'coat' is 'COMBAT'.
(Other definitions for combat that I've seen before include "Take action to deal with - fight" , "Fight against; fighting" , "sort of jacket" , "Fight, struggle or contest" , "Battle, warfare" .)