Rival after doctor in film (5)
I believe the answer is:
movie
'film' is the definition.
(I know that film can be written as movie)
'rival after doctor' is the wordplay.
'rival' becomes 'vie' (I've seen this in other clues).
'after' means one lot of letters go next to another.
'doctor' becomes 'mo' (medical officer).
'vie' put after 'mo' is 'MOVIE'.
'in' acts as a link.
(Other definitions for movie that I've seen before include "provide entertainment" , "one screened" , "picture" , "Flick" , "Gladiator for one" .)