Film finishes early -- drive away (4)
I believe the answer is:
shoo
'drive away' is the definition.
(shooing is a kind of driving away)
'film finishes early' is the wordplay.
'film' becomes 'shoot' (synonyms).
'finishes early' means to remove the last letter (the word finishes before its final letter).
'shoot' with its last letter taken away is 'SHOO'.
(Other definitions for shoo that I've seen before include "Expression to chase away an animal" , "Word used to frighten away animals" , "Begone!" , "Sound uttered to make animals go away" , "Exclamation used to chase away animals" .)