Brilliance of stone set in something attractive (6)
I believe the answer is:
lustre
'brilliance' is the definition.
(I've seen this before)
'stone set in something attractive' is the wordplay.
'stone' becomes 'st' (abbreviation).
'set in' means one lot of letters goes inside another.
'something attractive' becomes 'lure' (something which lures people).
'st' going inside 'lure' is 'LUSTRE'.
'of' is the link.
(Other definitions for lustre that I've seen before include "Soft brightness or glory" , "Gloss - type of pottery" , "brilliance" , "Radiance; reflective surface" , "Glory, distinction" .)