PVC (5)
I believe the answer is:
vinyl
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">pvc</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 vinyl that I've seen before include "Flexible plastic for flooring (or old records?)" , "LP material" , "Synthetic plastic" , "LP-making material" , "A plastic (LPs)" .)