Green gemstones (8)
I believe the answer is:
emeralds
'green gemstones' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for emeralds that I've seen before include "Green stones from strangely red males" , "They're preciously green on the Isle" , "Green gems" , "Colours" , "Precious stones for odd red males" .)