Brief appearance (5)
I believe the answer is:
cameo
'brief appearance' is the definition.
(brief appearance in a film)
This is the entire clue.
(Other definitions for cameo that I've seen before include "Jewellery item with carved portrait" , "Piece of jewellery with carved portrait" , "Carving in low relief" , "Small piece of carved stone or small role in play" , "Ornament or miniature performance" .)