You and I back film genre (7)
I believe the answer is:
western
'film genre' is the definition.
(I've seen this before)
'you and i back' is the wordplay.
'you and i' becomes 'we'.
'back' becomes 'stern' (I've seen this before).
'we'+'stern'='WESTERN'
(Other definitions for western that I've seen before include "Cowboys and Indians movie" , "Cowboys and Indians film" , "Spaghetti film?" , "Old film genre, horse opera" , "Type of film or music" .)