Most loud (8)
I believe the answer is:
noisiest
'most loud' is the definition.
('noisy' is associated in meaning with 'loud')
This is the entire clue.
(Other definitions for noisiest that I've seen before include "Making the loudest sounds" , "Making the most loud sounds" , "Making the most sound" , "party being at this extreme?" , "Most rowdy" .)