Nota bene: Indicate a source of water (4,4)

I believe the answer is:

mark well

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'nota bene' is the definition.
I know nothing about this answer so I cannot tell whether this works.

'indicate a source of water' is the wordplay.
'indicate' becomes 'mark' (marking is a kind of indicating).
'a source of water' becomes 'well' (water may come from a well).
'mark'+'well'='MARK WELL'

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

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