William in debt is like the waves (9)

I believe the answer is:

billowing

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'like the waves' is the definition.
I can't tell whether this defines the answer.

'william in debt' is the wordplay.
'william' becomes 'bill' ().
'in debt' becomes 'owing' (I've seen this before).
'bill'+'owing'='BILLOWING'

'is' is the link.

Can you help me to learn more?

(Other definitions for billowing that I've seen before include "affected by inflation" , "rolling in" .)

I've seen this clue in the Sydney Morning Herald.

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