Thickness, fold (3)
I believe the answer is:
ply
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">thickness</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >'<span class="explanation-format__original">fold</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for ply that I've seen before include "Fold; thickness" , "'Persist in offering, liquor say (3)'" , "A layer to work at diligently." , "This wood is laminated" , "drama one's missed" .)