Criterion, standard (10)
I believe the answer is:
touchstone
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">criterion</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that criterion can be written as touchstone)</span><br/ ><br/ >'<span class="explanation-format__original">standard</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that standard can be written as touchstone)</span><br/ ><br/ ></span>
(Other definitions for touchstone that I've seen before include "jester" , "Character in As You Like It" , "forest-dweller" , "Jasper" , "stage clown" .)