Small role for a big star (5)
I believe the answer is:
cameo
'small role for a big star' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for cameo that I've seen before include "Carving in relief, on a brooch say" , "Jewellery item with carved portrait" , "Jewellery item - small dramatic role" , "Part in movie" , "Piece of jewellery with carved portrait" .)