Note picture is a very long film, perhaps (4)
I believe the answer is:
epic
'a very long film perhaps' is the definition.
(an epic film)
'note picture' is the wordplay.
'note' becomes 'e' (musical note).
'picture' becomes 'pic' (short for picture).
'e'+'pic'='EPIC'
'is' is the link.
(Other definitions for epic that I've seen before include "On a grand scale, like heroic poem" , "Surpassing the ordinary" , "Long poem - awesome!" , "Long account" , "Film or book on a grand scale" .)