Open acknowledgement that there's no entrance fee (4,9)

I believe the answer is:

free admission

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'open acknowledgement that there's no entrance fee' is the definition.
The definition suggests a singular noun which matches the answer.

'open acknowledgement' is the wordplay.
'open' becomes 'free' (similar in meaning).
'acknowledgement' becomes 'admission' (admission is a kind of acknowledgement).
'free'+'admission'='FREE ADMISSION'

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

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