Nile snake (3)
I believe the answer is:
asp
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">nile snake</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for asp that I've seen before include "Snake, killed Cleopatra" , "Cleopatra's supposed nemesis" , "Reptile" , "Predatory fish" , "One secreting poison" .)