Treated to a parting observation (4,3)

I believe the answer is:

seen off

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'a parting observation' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'treated to' is the wordplay.
'treated' becomes 'seen' (I've seen this in another clue).
'to' becomes 'off' (I am not sure about this - if you are sure you should believe this answer much more).
'seen'+'off'='SEEN OFF'

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I've seen this clue in the Evening Standard.

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