Smooth glossy fabric
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">smooth glossy fabric</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for satin that I've seen before include "Silky material" , "Rich cloth" , "Smooth and silky" , "Fine material" , "Glossy textile" .)