A small role that came to nothing (5)
I believe the answer is:
cameo
'a small role' is the definition.
(I've seen this before)
'came to nothing' is the wordplay.
'to nothing' becomes 'o' (looks like zero - 0).
'came'+'o'='CAMEO'
'that' acts as a link.
(Other definitions for cameo that I've seen before include "Star's tiny role" , "Brooch with an engraving in low relief" , "Carving in relief, on a brooch say" , "Small part for star actor" , "Brief role" .)