Be fully aware that you are no stranger to (4,4)

I believe the answer is:

know well

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'aware that you are no stranger to' is the definition.
I don't know anything about this answer so I can't judge whether this works.

'be fully' is the wordplay.
'be' becomes 'know' (I am not sure about this - if you are sure you should believe this answer much more).
'fully' becomes 'well' (synonyms).
'know'+'well'='KNOW WELL'

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I've seen this clue in the Evening Standard.

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