Thorn in one's side
I believe the answer is:
bane
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">thorn in one's side</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for bane that I've seen before include "Cause of distress, ruin" , "Something causing misery or distress" , "Source of misery" , "Cause of trouble or worry, like bean" , "Cause of great distress in a bean" .)