Unit of prevention
I believe the answer is:
ounce
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">unit of prevention</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 ounce that I've seen before include "There are quite a few in the pound" , "Weight; big cat" , "Wild cat or light weight" , "little weight" , "Unit of weight; cat" .)