Celebrity overturned vermin (4)
I believe the answer is:
rats
'vermin' is the definition.
(I've seen this in another clue)
'celebrity overturned' is the wordplay.
'celebrity' becomes 'star' (a star is a celebrity or famous person).
'overturned' is a reversal indicator.
'star' written backwards gives 'RATS'.
(Other definitions for rats that I've seen before include "Mild oath - sewer residents" , "were piped away" , "Snoopy's imprecation - vermin" , "Tells" , "(Hunts) rodents - expression of irritation" .)