Pit viper (10)
I believe the answer is:
copperhead
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">pit viper</span>' is the definition.<br/ ><span class="explanation-format__explanation">(copperhead is a kind of pit viper)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for copperhead that I've seen before include "venomous sort" , "Venomous type" , "Reptile" , "Venomous, reddish-brown American snake" , "Highly venomous US or Australian snake" .)