Fine cotton fabric (6)
I believe the answer is:
muslin
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fine cotton fabric</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 muslin that I've seen before include "Gauze-like cloth" , "Fine soft plain-woven cotton fabric of gauzy appearance" , "Lightweight cotton fabric" , "Cotton for veil or strainer" , "Lightweight cotton cloth" .)