Endless street party -- turn up the volume! (9)
I believe the answer is:
crescendo
'turn up the volume' is the definition.
(to crescendo is to increase in loudness)
'endless street party' is the wordplay.
'endless' means to remove the last letter.
'street' becomes 'crescent' (No).
'party' becomes 'do' (do is a kind of party).
'crescent' with its last letter removed is 'crescen'.
'crescen'+'do'='CRESCENDO'
(Other definitions for crescendo that I've seen before include "Gradual increase in volume" , "Intensify" , "Rising noise" , "Gradual loudening" , "Growing louder (mus.)" .)