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 "one stirring things up", "one causing a stir", "subversive", "Subversive person", "stirrer", "Rabble-rouser - blender", "Trouble-maker, he stirs things up", "Person who stirs up trouble", "One causing trouble" and "Agent provocateur".)