Doctor to compete for picture (5)
I believe the answer is:
movie
'picture' is the definition.
('movie' can be a synonym of 'picture')
'doctor to compete' is the wordplay.
'doctor' becomes 'mo' (medical officer).
'to compete' becomes 'vie' ('vie' can be a synonym of 'compete').
'mo'+'vie'='MOVIE'
'for' acts as a link.
(Other definitions for movie that I've seen before include "Cinema film (mainly US)" , "Gladiator for one" , "picture" , "Cinema production" , "one screened" .)