Jewelry stone (3)
I believe the answer is:
gem
'jewelry stone' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for gem that I've seen before include "A precious stone like a diamond or emerald etc" , "36 Across or any other jewel" , "Valuable stone" , "Emerald or sapphire, say" , "Diamond, ruby, or emerald" .)