Small acting role (3,4)
I believe the answer is:
bit part
'small acting role' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for bit part that I've seen before include "cameo" , "Tiny or non-speaking dramatic role" , "Very minor role" , "extra work, perhaps" , "Tiny or non-speaking role in play" .)