Correct film certificate (6)
I believe the answer is:
ticket
'certificate' is the definition.
(thesaurus)
'correct film' is the wordplay.
'correct' becomes 'tick' (a tick is used to mark an answer correct).
'film' becomes 'et'.
'tick'+'et'='TICKET'
(Other definitions for ticket that I've seen before include "Slip showing payment of entrance fee" , "Party's election policies; label" , "Tag showing fare or fee" , "Admission card" , "Permit to do something" .)