The wife's bet? (6-4)

I believe the answer is:

better-half

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

'the wife's' is the definition.
(I've seen this before)

'bet?' is the wordplay.
I cannot quite understand how this works, but
'bet?' could be 'bet' and 'bet' is found in 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 Sydney Morning Herald.

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