Animals' star turn (4)
I believe the answer is:
rats
'animals'' is the definition.
(rat is a kind of animal)
'star turn' is the wordplay.
'turn' says the letters should be written backwards.
'star' written backwards gives 'RATS'.
(Other definitions for rats that I've seen before include "Heels" , "Oh no" , "Blast" , "Mild oath - sewer residents" , "Damn" .)