Star's bit part (5)
I believe the answer is:
cameo
'star's bit part' 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 "Small but interesting role" , "Short performance" , "Brooch with an engraving in low relief" , "Item of jewellery with a portrait - distinguished actor's minor role" , "Part in movie" .)