Are you going to pay up? I won't ask you again! (4,6)

I believe the answer is:

last demand

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'are you going to pay up? i won't' is the definition.
I don't know anything about this answer so I can't tell whether this works.

'ask you again' is the wordplay.
I cannot quite see how this works, but
'ask' could be 'demand' (synonyms) and 'demand' is found in the answer.
The remaining letters 'last' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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