Dealing with snack, having prolonged success (7)

I believe the answer is:

onaroll

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'snack having prolonged success' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'dealing with' is the wordplay.
I cannot really understand how this works, but
'dealing with' could be 'on' and 'on' is located in the answer.
This explanation may well be incorrect...

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I've seen this clue in The Daily Express.

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