Banded gemstones (6)
I believe the answer is:
agates
'banded gemstones' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for agates that I've seen before include "Ste aga up for the stones" , "Chalcedonies" , "Stones to be found in a stage" , "Hard coloured stones from a stage" , "Banded semiprecious stones" .)