Show long film in empty depot (6)
I believe the answer is:
depict
'show' is the definition.
('depict' can be a synonym of 'show')
'long film in empty depot' is the wordplay.
'long film' becomes 'epic' (I've seen this before).
'in' is an insertion indicator.
'empty' means to remove the middle letters.
'depot' with its middle removed is 'dt'.
'epic' inserted inside 'dt' is 'DEPICT'.
(Other definitions for depict that I've seen before include "Sketch or describe" , "Paint" , "Make portrait" , "Show in form of picture, or describe in words" , "Portray, represent" .)