Snack in trolley (4)

I believe the answer is:

roll

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'snack' is the definition.
The answer and definition can be both things that one consumes for nourishment as well as being singular nouns.
Perhaps there's a link between them I don't understand?

'in trolley' is the wordplay.
'in' says the answer is hidden in the clue.
'ROLL' is hidden within 'trolley'.

Can you help me to learn more?

(Other definitions for roll that I've seen before include "on which one is regularly successful" , "Swell" , "Bread - list - drumbeats" , "Schedule" , "Bun" .)

I've seen this clue in The Mirror.

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