Snack in trolley (4)
I believe the answer is:
roll
'snack' is the definition.
The answer and definition can be both things that one consumes for nourishment as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'in trolley' is the wordplay.
'in' indicates a hidden word.
'ROLL' is hidden in the letters of '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" .)