Propose to take in one film (5)
I believe the answer is:
movie
'film' is the definition.
('movie' can be a synonym of 'film')
'propose to take in one' is the wordplay.
'propose' becomes 'move' (moving is a kind of proposing**).
'to take in' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'move' enclosing 'i' is 'MOVIE'.
(Other definitions for movie that I've seen before include "Cinema film (mainly US)" , "one screened" , "provide entertainment" , "Gladiator for one" , "Flick" .)