Crossword Genius

Water supply is exhausted but was used profitably (4-5)

Ross

I believe the answer is:

well-spent

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'was used profitably' is the definition.
I can't judge whether this defines the answer.

'water supply is exhausted' is the wordplay.
'water supply' becomes 'well' (a well is a source of water).
'is exhausted' becomes 'spent' (synonyms).
'well'+'spent'='WELL-SPENT'

'but' is the link.

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I've seen this clue in The Globe and Mail.
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