Simple addition to contract for film (4,5)
I believe the answer is:
easy rider
'film' is the definition.
(I've seen this before)
'simple addition to contract' is the wordplay.
'simple' becomes 'easy' ('easy' is associated in meaning with 'simple').
'addition to contract' becomes 'rider' (additional clause on a contract).
'easy'+'rider'='EASY RIDER'
'for' is the link.
(Other definitions for easy rider that I've seen before include "Picture" , "Film about motor cyclists' travels" , "Nineteen sixty-nine road movie (Hopper, Nicholson)" , "1969 road movie" , "Peter Fonda film" .)