Actor's chaff at a party (6)
I believe the answer is:
brando
'actor's' is the definition.
(I've seen this before)
'chaff at a party' is the wordplay.
'chaff' becomes 'bran' (bran is a kind of chaff).
'at' is a charade indicator (letters next to each other).
'a party' becomes 'do' (do is a kind of party).
'bran'+'do'='BRANDO'
(Other definitions for brando that I've seen before include "'The Godfather'?" , "Actor who died this year" , "heart-throb" , "Marlon . . . . . ., star of ''On The Waterfront'' (6)" , "actor in 4 26 21 [A STREETCAR NAMED DESIRE]" .)