Brave, turning up the radio a bit (4)
I believe the answer is:
dare
'brave' is the definition.
(thesaurus)
'turning up the radio a bit' is the wordplay.
'turning up' says the letters should be written backwards.
'a bit' indicates a hidden word (the answer is formed by a bit of the clue).
'erad' is hidden within 'the radio'.
'erad' backwards is 'DARE'.
(Other definitions for dare that I've seen before include "Venture, have courage" , "Challenge to do something dangerous" , "Be brave enough" , "Have the courage to try something" , "Have sufficient courage" .)