Tooth layer (6)
I believe the answer is:
enamel
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tooth layer</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for enamel that I've seen before include "Outer tooth material" , "Decorative inlay" , "canine protection?" , "Shiny coat as on teeth" , "Hard substance covering teeth" .)