Making money from a gulf in supply (7)

I believe the answer is:

gainful

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'making money from' is the definition.
I can't tell whether this definition defines the answer.

'a gulf in supply' is the wordplay.
'supply' is an anagram indicator (in a supple way).
'a'+'gulf'+'in'='agulfin'
'agulfin' with letters rearranged gives 'GAINFUL'.

Can you help me to learn more?

(Other definitions for gainful that I've seen before include "Bringing in money" , "Profitable and productive" .)

I've seen this clue in The Times and The Sunday Times.

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