Stable mate
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">stable mate</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 mare that I've seen before include "For classicists, sea" , "Nag" , "Female equine animal" , "A night-time strangler" , "Adult female horse" .)