A very loud tune associated with love (6)
I believe the answer is:
affair
'love' is the definition.
(thesaurus)
'a very loud tune associated with' is the wordplay.
'very loud' becomes 'ff' (musical abbreviation for 'fortissimo', very loud).
'tune' becomes 'air' (air can mean a piece of music).
'associated with' is a charade indicator (letters next to each other).
'a'+'ff'+'air'='AFFAIR'
(Other definitions for affair that I've seen before include "Extramarital activity" , "Romantic relationship between two unmarried people" , "Singular business" , "Sexual liaison - concern" , "Concern (maybe extra-marital?)" .)