Bit part for a star (5)
I believe the answer is:
cameo
'bit part for a star' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cameo that I've seen before include "Piece of jewellery with carved portrait" , "Jewellery item with carved portrait" , "Small piece of hard stone carved with raised design" , "Star's tiny role" , "Something small but well done - say role in play" .)