Ring with lithium-infused glass resembling a gem (7)
I believe the answer is:
opaline
'glass resembling a gem' is the definition.
I can't judge whether this definition defines the answer.
'ring with lithium-infused' is the wordplay.
'ring' becomes 'O' (letter resembling a ring).
'with' is an insertion indicator.
'lithium' becomes 'Li' (Li is the chemical symbol for lithium).
'infused' becomes 'pane' (I can't explain this - if you can you should give a lot more credence to this answer).
'li' put within 'pane' is 'paline'.
'o'+'paline'='OPALINE'
Can you help me to learn more?
(Other definitions for opaline that I've seen before include "white!" , "of stones" , "Photographic plate" , "not entirely clear" , "Milk glass" .)