Discussion subject in honour of film (5)
I believe the answer is:
topic
'discussion subject' is the definition.
(I've seen this in another clue)
'in honour of film' is the wordplay.
'in honour of' becomes 'to' ('to' can mean dedicated to or in honour of).
'film' becomes 'pic' (short for picture).
'to'+'pic'='TOPIC'
(Other definitions for topic that I've seen before include "Theme (of, eg, a talk)" , "A subject for conversation or debate" , "Matter for an argument" , "Subject (for conversation, etc)" , "might this be hot?" .)