Gem in a clam (5)
I believe the answer is:
pearl
(Other definitions for pearl that I've seen before include "Gem from a bivalve" , "Precious stone from shellfish" , "greatly valued" , "Girl < , pretty" , "Off-white colour" .)
I believe the answer is:
pearl
(Other definitions for pearl that I've seen before include "Gem from a bivalve" , "Precious stone from shellfish" , "greatly valued" , "Girl < , pretty" , "Off-white colour" .)