Again but for the last time presumably (4,4)

I believe the answer is:

once more

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'again' is the definition.
(synonyms)

'for the last time presumably' is the wordplay.
I cannot really understand how this works, but
'time' could be 'once' (I have seen 'Single time ' mean 'once' so perhaps 'time' could also mean 'once') and 'once' is found within the answer.
The remaining letters 'more' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

'but' is the link.

Can you help me to learn more?

(Another definition for once more that I've seen is " Again".)

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

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