Fitting offer on film (5)
I believe the answer is:
bidet
'fitting' is the definition.
(bathroom fitting)
'offer on film' is the wordplay.
'offer' becomes 'bid' (synonyms).
'on' says to put letters next to each other.
'film' becomes 'ET' (E.T. the Extra-Terrestrial).
'bid'+'et'='BIDET'
(Other definitions for bidet that I've seen before include "bathroom accessory" , "Low basin for washing private parts" , "bathroom installation" , "Washing facility" , "Cleaning vessel for privates" .)