Loud tune in entertainment event (4)
I believe the answer is:
fair
'entertainment event' is the definition.
(eg a fun fair)
'loud tune' is the wordplay.
'loud' becomes 'f' (short for forte - 'loud' in music).
'tune' becomes 'air' (air can mean a piece of music).
'f'+'air'='FAIR'
'in' acts as a link.
(Other definitions for fair that I've seen before include "Just; fete" , "Equitable ? - trade show" , "Traders' gathering" , "Equitable - market - not bad" , "Beautiful; exhibition" .)