A small part of relief work (5)
I believe the answer is:
cameo
I believe this clue is a double definition.
'a small part' is the first definition.
(small part in a film)
'relief work' is the second definition.
(I've seen this before)
'of' acts as a link.
(Other definitions for cameo that I've seen before include "Piece of jewellery; small role" , "Small but interesting role" , "Small role in film" , "Part in movie" , "Carved brooch - small role" .)