Smooth or glossy fabric (5)
I believe the answer is:
satin
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">smooth</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >'<span class="explanation-format__original">glossy fabric</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for satin that I've seen before include "Stain on shiny fabric" , "Silky material" , "Smooth and silky" , "Stain on shiny cloth" , "Material with glossy front and dull back" .)