Bugbear, bête noire (4)
I believe the answer is:
bane
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">bugbear</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >'<span class="explanation-format__original">bete noire</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for bane that I've seen before include "Affliction, cause of distress" , "Source of misery" , "it causes misery" , "Something causing misery or distress" , "Cause of great distress, rhymes with rule" .)