Arthur's queen (9)
I believe the answer is:
guinevere
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">arthur's queen</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 guinevere that I've seen before include "Arthur's wife (and Lancelot's lover?)" , "legendary wife" , "Unfaithful queen" , "legendary character)" , "A mistress" .)