Vertebrates (8)
I believe the answer is:
reptiles
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">vertebrates</span>' is the definition.<br/ ><span class="explanation-format__explanation">(reptile is a kind of vertebrate)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for reptiles that I've seen before include "Cold-blooded vertebrates" , "Snakes, lizards etc." .)