Doctor training causes misery (4)
I believe the answer is:
mope
'misery' is the definition.
(I've seen this before)
'doctor training' is the wordplay.
'doctor' becomes 'mo' (medical officer).
'training' becomes 'PE' (short for Physical Education).
'mo'+'pe'='MOPE'
'causes' acts as a link.
(Other definitions for mope that I've seen before include "Be mildly depressed" , "listless person" , "Be listless and apathetic" , "Pine - sulk" , "Be listless over poem" .)