It's unusual for a Manx cat to make a lot of noise (6)
I believe the answer is:
rumpus
'noise' is the definition.
(thesaurus)
'it's unusual for a manx cat' is the wordplay.
'it's unusual' becomes 'rum' (I've seen this before).
'for' says to put letters next to each other.
'a manx' means to remove the last letter (Manx cats have no tail).
'cat' becomes 'puss' (puss is a kind of cat).
'puss' with its last letter taken off is 'pus'.
'rum'+'pus'='RUMPUS'
'to make a lot of' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for rumpus that I've seen before include "Row" , "'Commotion, din (6)'" , "Noisy brawl" , "5a [BALLYHOO] involving noise" , "Harsh rough nature" .)