Precious stone given by a fellow on date in bar (9)
I believe the answer is:
almandine
'precious stone' is the definition.
'a fellow on date in bar' is the wordplay.
'a fellow' becomes 'man' (fellow can mean a man).
'on' means one lot of letters goes inside another.
'date in bar' becomes 'aldine' (I can't explain this - if you can you should believe this answer much more).
'man' going into 'aldine' is 'ALMANDINE'.
'given by' acts as a link.
Can you help me to learn more?
(Another definition for almandine that I've seen is " jewellery".)