Want work on radio (4)
I believe the answer is:
need
'want' is the definition.
(I know that want can be written as need)
'work on radio' is the wordplay.
'work' becomes 'knead' (synonyms).
'on radio' indicates a 'sounds like' (homophone) clue.
'knead' sounds like 'NEED'.
(Other definitions for need that I've seen before include "Exigency" , "Require (as essential)" , "Want - require(ment)" , "state of distress" , "Shortage" .)