Light but loud music (4)
I believe the answer is:
fair
'light' is the definition.
(I've seen this in another clue)
'loud music' is the wordplay.
'loud' becomes 'f' (short for forte - 'loud' in music).
'music' becomes 'air' (air is a kind of music).
'f'+'air'='FAIR'
'but' is the link.
(Other definitions for fair that I've seen before include "legitimate" , "Blonde; impartial" , "Equitable; expo" , "Equitable - market - not bad" , "Beautiful; exhibition" .)