Old maid in Tchaikovsky opera? (5,2,6)

I believe the answer is:

queen of spades

I'm a little stuck... Click here to teach me more about this clue!

This might be a double definition.

'old maid' is the first definition.
Both the definition and answer are singular nouns.
Perhaps you can see a link between them that I can't see?

'tchaikovsky opera?' is the second definition.
The definition suggests a singular noun which matches the answer.

'in' acts as a link.

Can you help me to learn more?

I've seen this clue in The Irish Times.

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