Diamonds wow, encrusted with proper gemstone (3,5)

'gemstone' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

'diamonds wow encrusted with proper' is the wordplay.
I cannot really understand how this works, but
'diamonds' could be 'd' (abbreviation in bridge say) and 'd' is found within the answer.
'wow' could be 'cor' (both are expressions of surprise) and 'cor' is found in the answer.
'proper' could be 'real' (similar in meaning) and 'real' is found in the remaining letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?