Gem from an oyster (5)
I believe the answer is:
pearl
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">gem from an oyster</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for pearl that I've seen before include "White - jewel" , "Off-white colour" , "Paragon" , "Precious stone from shellfish" , "one regularly in stitches" .)