Small role arrived with Oscar (5)
I believe the answer is:
cameo
'small role' is the definition.
(I've seen this before)
'arrived with oscar' is the wordplay.
'arrived' becomes 'came' (come can mean to appear or arrive).
'with' is a charade indicator (letters next to each other).
'oscar' becomes 'O' (phonetic alphabet: alpha, bravo, charlie etc.).
'came'+'o'='CAMEO'
(Other definitions for cameo that I've seen before include "Carved brooch - small role" , "Small role - gem with a figure carved in relief" , "Item of jewellery with a portrait - distinguished actor's minor role" , "Something small but well executed, say role in play" , "E. Med. nation" .)