'Piano' film actor (6)
I believe the answer is:
player
'actor' is the definition.
(I know that actor can be written as player)
'piano film' is the wordplay.
'piano' becomes 'p' (musical abbreviation).
'film' becomes 'layer' (film can mean a thin layer of something).
'p'+'layer'='PLAYER'
(Other definitions for player that I've seen before include "Actor - footballer?" , "Batsman perhaps" , "Participant in soccer match or other game" , "Game's participant" , "Important participant" .)