Girls originally employed in banks look at ornamental gem (6-3)
I believe the answer is:
tigers-eye
'ornamental gem' is the definition.
The definition suggests a singular noun which matches the answer.
'girls originally employed in banks look at' is the wordplay.
'girls originally' becomes 'g' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'employed in' indicates putting letters inside.
'banks' becomes 'tiers' (I've seen this in another clue).
'look at' becomes 'eye' (I've seen this before).
'g' put within 'tiers' is 'tigers'.
'tigers'+'eye'='TIGERS-EYE'
Can you help me to learn more?
(Another definition for tigers-eye that I've seen is " Yellow-brown gemstone".)