Stone set on ring given to friend (4)
I believe the answer is:
opal
'stone set' is the definition.
'opal' can be an answer for 'stone' (gemstone). I am not certain of the 'set' bit.
'ring given to friend' is the wordplay.
'ring' becomes 'O' (O is the shape of a ring).
'given to' says to put letters next to each other.
'friend' becomes 'pal' (pal can mean a friend).
'o'+'pal'='OPAL'
'on' is the link.
Can you help me to learn more?
(Other definitions for opal that I've seen before include "Glassy gemstone" , "One's stony" , "Semi-precious stone of b;uish white colour" , "Semi-transparent gemstone" , "Milky-white gem" .)