You and I put on grim movie (7)
I believe the answer is:
western
'movie' is the definition.
(Western is an example)
'you and i put on grim' is the wordplay.
'you and i' becomes 'we'.
'put on' means one lot of letters go next to another.
'grim' becomes 'stern' ('stern' can be a synonym of 'grim').
'we'+'stern'='WESTERN'
(Other definitions for western that I've seen before include "Cowboy film of occidental origin" , "Old film genre, horse opera" , "Spaghetti film?" , "Cowboys and Indians movie" , "direction?" .)