Solidifying (7)
I believe the answer is:
setting
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">solidifying</span>' is the definition.<br/ ><span class="explanation-format__explanation">(setting is a kind of solidifying)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for setting that I've seen before include "Writing puzzles, perhaps" , "Environment" , "Mount for gem" , "Surroundings; hardening" , "making up a crossword puzzle" .)