Kind of cat or butterfly (13)
I believe the answer is:
tortoiseshell
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">kind of cat</span>' is the first definition.<br/ ><br/ >'<span class="explanation-format__original">butterfly</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(tortoiseshell is a kind of butterfly)</span><br/ ><br/ ></span>
(Other definitions for tortoiseshell that I've seen before include "Ornamental material" , "Domestic cat mottled in brownish-yellow and black" , "Domestic cat - or little shoes (anag)" , "Butterfly - cat" , "The case of the slow-moving" .)