Keep in mind payment for use of the port (7,4)

I believe the answer is:

harbour dues

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'use of the port' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'keep in mind payment' is the wordplay.
'keep' becomes 'harbour' (harbouring is a kind of keeping).
'in mind payment' becomes 'dues' (I can't explain this - if you can you should believe this answer much more).
'harbour'+'dues'='HARBOUR-DUES'

'for' is the link.

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

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