Long film shown in the pictures (4)
I believe the answer is:
epic
'long film' is the definition.
(I've seen this before)
'in the pictures' is the wordplay.
'in' indicates a hidden word.
'EPIC' can be found hidden inside 'the pictures'.
'shown' acts as a link.
(Other definitions for epic that I've seen before include "Of heroic proportions" , "Guardian (body, beast)" , "A long poem or book with adventurous theme" , "Blown up" , "of impressive proportions?" .)