Mosaic tile (7)
I believe the answer is:
tessera
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mosaic tile</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for tessera that I've seen before include "part of a mosaic" , "small bit of artwork" , "Mosaic component" , "Mosaic stone" , "Bit of mosaic" .)