Nile serpent (3)
I believe the answer is:
asp
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">nile serpent</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 asp that I've seen before include "creeper" , "A glider's what's called for" , "Reptile" , "Snake seen in a spa, strangely" , "Joe Blake is Australian species" .)