One who succeeds on radio broadcast (3)
I believe the answer is:
air
'broadcast' is the definition.
(to air on TV)
'one who succeeds on radio' is the wordplay.
'one who succeeds' becomes 'heir' (I've seen this before).
'on radio' indicates a 'sounds like' (homophone) clue.
'heir' is a homophone of 'AIR'.
(Other definitions for air that I've seen before include "Light breeze" , "put on radio?" , "Ventilate with oxygen" , "Bearing, manner" , "Of which 78% is nitrogen" .)