Tooth surface (6)
I believe the answer is:
enamel
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tooth surface</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 enamel that I've seen before include "Hard gloss paint" , "Ale men (anag.)" , "sort of paint" , "hard cover" , "Shiny layer on surface" .)