Crossword Genius

Lady, one potentially a queen, we're told (3)

Ross

I believe the answer is:

bea

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

'lady' is the definition.

'one potentially a queen we're told' is the wordplay.
I cannot really see how this works, but
'one' could be 'a' (a thing is one thing) and 'a' is found in the answer.
The remaining letters 'be' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in The Times.
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