Crossword Genius

Change one's bank maybe (5,4)

Ross

I believe the answer is:

cross over

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

'bank maybe' is the definition.
The definition suggests a singular noun which matches the answer.

'change one's' is the wordplay.
I cannot quite understand how this works, but
'one's' could be 'os' (I've seen this in other clues) and 'os' is found within the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in The Globe and Mail.
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