Vipers (6)
I believe the answer is:
adders
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">vipers</span>' is the definition.<br/ ><span class="explanation-format__explanation">(adder is a kind of viper)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for adders that I've seen before include "Do they deal with tots" , "sum? We do" , "Snakes are totters" , "Venomous snakes" , "Totting 25 down?" .)