Came to love a tiny role (5)
I believe the answer is:
'a tiny role' is the definition.
(I've seen this in another clue)
'came to love' is the wordplay.
'to love' becomes 'o' (love means zero in tennis).
(Other definitions for cameo that I've seen before include "Something small but well done - say role in play" , "relief work" , "E. Med. nation" , "Something small but well executed, say role in play" , "Small part for star actor" .)