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