More clamorous number on island that's finally calmer (7)
I believe the answer is:
noisier
'more clamorous' is the definition.
('noisy' can be similar in meaning to 'clamorous')
'number on island that's finally calmer' is the wordplay.
'number' becomes 'noise' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'on' is an insertion indicator (as in clothing 'on' a person).
'island' becomes 'i'.
'that's finally' says to take the final letters.
The last letter of 'calmer' is 'r'.
'noise' going around 'i' is 'noisie'.
'noisie'+'r'='NOISIER'
Can you help me to learn more?
(Other definitions for noisier that I've seen before include "Less quiet" , "More rowdy" , "More of a racket" , "Louder" , "Perhaps more disturbing" .)