Unemployed star on radio (4)
I believe the answer is:
Here is my best explanation:
'unemployed' is the definition.
('idle' can be similar in meaning to 'unemployed')
'star on radio' is the subsidiary indication.
'star' becomes 'idol' (idol is a kind of star).
'on radio' indicates a 'sounds like' (homophone) clue.
'idol' is a homophone of 'idle'.
(Other definitions for idle that I've seen before include "Monty Python team member", "without basis", "Circus entertainer", "Lied about doing nothing", "Of engine, tick over", "Trivial", "Good-for-nothing", "Not occupied", "Unemployed" and "loiter aimlessly".)