Celebrity traitors' revolution (4)
I believe the answer is:
star
'celebrity' is the definition.
(a star is a celebrity or famous person)
'traitors' revolution' is the wordplay.
'traitors'' becomes 'rats' (rat can mean a traitor).
'revolution' says the letters should be written in reverse.
'rats' backwards is 'STAR'.
(Other definitions for star that I've seen before include "Symbol of excellence" , "Pointed shape" , "feature in film" , "Arts (anag)" , "Outstanding entertainer" .)