Star turn by rotters (4)
I believe the answer is:
rats
'rotters' is the definition.
('rat' can be a synonym of 'rotter')
'star turn' is the wordplay.
'turn' says the letters should be written in reverse.
'star' written backwards gives 'RATS'.
'by' acts as a link.
(Other definitions for rats that I've seen before include "Annoyed expression" , "Blast" , "Hamelin's pests" , "Damn" , "Snoopy's imprecation - vermin" .)