Can you bank on her being one's better half? (3)

I believe the answer is:

bet

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

'better half?' is the definition.

I cannot understand how the remainder of the clue works.

(Other definitions for bet that I've seen before include "Speculation" , "Wager, speculate" , "Wager, back" , "Money risked on a gamble" , "22 across will accept one" .)

I've seen this clue in the Evening Standard.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.