Harden; group (3)
I believe the answer is:
set
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">harden</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(set can mean to go hard or dry)</span><br/ ><br/ >'<span class="explanation-format__original">group</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(both can mean a collection)</span><br/ ><br/ ></span>
(Other definitions for set that I've seen before include "exclusive party" , "Cake < , plonk < , something served" , "Solidify like jelly" , "Prescribed" , "decline" .)