Enjoying continuing success playing a character on the radio (2,1,4)
I believe the answer is:
on a roll
'enjoying continuing success' is the definition.
(I've seen this before)
'playing a character on the radio' is the wordplay.
'playing' becomes 'on' (on can mean playing or performing).
'character' becomes 'role' (synonyms).
'on the radio' indicates a 'sounds like' (homophone) clue.
'role' sounds like 'roll'.
'on'+'a'+'roll'='ON A ROLL'
(Other definitions for on a roll that I've seen before include "enjoying continuing success" , "thus far unbeaten competitor?" , "enjoying lots of success" , "keeps having repeated wins" , "Having a run of success" .)