Thin layer or plate (6)
I believe the answer is:
lamina
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">thin layer</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">plate</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(anatomical term for a plate or layer)</span><br/ ><br/ ></span>
(Other definitions for lamina that I've seen before include "Flat plate" , "Thin plate or layer" , "Thin plate or scale" .)