Jazz fans getting half of performers rejected (4)
I believe the answer is:
cats
'jazz fans' is the definition.
(I've seen this in another clue)
'getting half of performers rejected' is the wordplay.
'getting' becomes 'ca' (I can't explain this - if you can you should give a lot more credence to this answer).
'half of' suggests halving the letters.
'performers' becomes 'cast' (I've seen this before).
'rejected' says the letters should be written backwards.
'cast' with half the letters taken is 'st'.
'st' in reverse letter order is 'ts'.
'ca'+'ts'='CATS'
(Other definitions for cats that I've seen before include "Musical from TS Eliot" , "Famous feline Lloyd Webber musical" , "Popular musical" , "Pets - musical" , "Carnivores - stage musical" .)