Tiara got damaged by incendiary (8)
I believe the answer is:
Here is my best explanation:
'incendiary' is the definition.
'tiara got damaged' is the subsidiary indication.
'damaged' is an anagram indicator.
'tiaragot' with letters rearranged gives 'agitator'.
'by' is the link.
(Other definitions for agitator that I've seen before include "Person who stirs up trouble", "Fomenter of unrest", "Got tiara for a trouble-maker", "Political troublemaker", "Disturber of the peace", "He stirs things up, causes trouble", "Trouble-maker, he stirs things up", "One fomenting trouble", "Provocateur or rabble-rouser" and "Person stirring up public feeling".)