Crossword Genius

How river flooding is costing a fortune? (8,3,4)

Ross

I believe the answer is:

breaking the bank

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

'fortune?' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'how river flooding is costing a' is the wordplay.
I cannot really see how this works, but
'river' could be 'ea' (I've seen this in other clues) and 'ea' is located in the answer.
'a' could be 'an' and 'an' is found within the answer.
This may be the basis of 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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