Tooth covering (6)
I believe the answer is:
enamel
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tooth covering</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 glossy surface" , "found on crowns" , "Hard shiny coating as on teeth" , "Crown Protector?" , "Hard white substance covering the crown of a tooth" .)