Source of annoyance (8)
I believe the answer is:
irritant
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">source of annoyance</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for irritant that I've seen before include "Cause of itch" , "Something that annoys, a nuisance" , "distraction" , "Annoying thing" , "causing annoyance" .)