Tiara got damaged by this troublemaker (8)
I believe the answer is:
agitator
'this troublemaker' is the definition.
(agitator is a kind of troublemaker)
'tiara got damaged' is the wordplay.
'damaged' indicates an anagram.
'tiara'+'got'='tiaragot'
'tiaragot' anagrammed gives 'AGITATOR'.
'by' acts as a link.
(Other definitions for agitator that I've seen before include "One whipping up concern" , "One stirring up (things)" , "Agent provocateur" , "cause of trouble" , "one causing disturbance" .)