Tiny opening in the skin (4)
I believe the answer is:
pore
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tiny opening in the skin</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for pore that I've seen before include "Minute passage in skin" , "Small opening in the skin" , "Minute opening in the skin" , "Rope around tiny hole" , "Rope around the skin-opening" .)