You and I join severe film (7)
I believe the answer is:
western
'film' is the definition.
(I know that Western is a type of long film)
'you and i join severe' is the wordplay.
'you and i' becomes 'we'.
'join' is a charade indicator (letters next to each other).
'severe' becomes 'stern' (I've seen this in another clue).
'we'+'stern'='WESTERN'
(Other definitions for western that I've seen before include "Cowboys and Indians movie" , "direction?" , "Spaghetti film?" , "Cowboys and Indians film" , "American film" .)