Fighting? Doctor having one put in bed (6)
I believe the answer is:
combat
'fighting?' is the definition.
('combat' can be a synonym of 'fighting')
'doctor having one put in bed' is the wordplay.
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus**).
'having' is a charade indicator (letters next to each other).
'one' becomes 'a'.
'put in' means one lot of letters goes inside another.
'bed' becomes 'cot' (cot is a kind of bed).
'mb'+'a'='mba'
'mba' placed within 'cot' is 'COMBAT'.
(Other definitions for combat that I've seen before include "A fight or contest, sometimes mortal" , "Military fighting" , "Fight - strive against" , "Fight against; fighting" , "Battle or fight" .)