Jazz fans' musical (4)
I believe the answer is:
cats
'musical' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
(Other definitions for cats that I've seen before include "1981 Lloyd Webber musical" , "Some 6 Downs" , "Spectacular Llyod Webber feline musical" , "Musical; jazz fans" , "Show" .)