Celebrity scoundrels on the rise (4)
I believe the answer is:
star
'celebrity' is the definition.
(I've seen this before)
'scoundrels on the rise' is the wordplay.
'scoundrels' becomes 'rats'.
'on the rise' says the letters should be written backwards.
'rats' in reverse letter order is 'STAR'.
(Other definitions for star that I've seen before include "may be a dwarf or a giant" , "appear above others?" , "feature in film" , "White blaze on a horse's forehead" , "eg The sun" .)