More cacophonous (7)
I believe the answer is:
noisier
'more cacophonous' is the definition.
('noisy' is associated in meaning with 'cacophonous')
This is the entire clue.
(Other definitions for noisier that I've seen before include "More loud" , "more deafening!" , "Louder" , "Less quiet" , "More rowdy" .)