Interminable street party growing louder (9)
I believe the answer is:
crescendo
'growing louder' is the definition.
(musical term)
'interminable street party' is the wordplay.
'interminable' means to remove the last letter (without the letter which terminates the word).
'street' becomes 'crescent' (crescent-shaped street).
'party' becomes 'do' (do is a kind of party).
'crescent' with its final letter taken off is 'crescen'.
'crescen'+'do'='CRESCENDO'
(Other definitions for crescendo that I've seen before include "Gradual increase in loudness, musically" , "Becoming louder in soccer den" , "Building up of sound" , "increase in sound level" , "rising from piano?" .)