Jam in snack (8)
I believe the answer is:
sandwich
This clue could be a double definition.
'jam in' is the first definition.
The definition and answer can be both things that one consumes for nourishment as well as being singular nouns.
Maybe there's an association between them I don't understand?
'snack' is the second definition.
(I've seen this before)
Can you help me to learn more?
(Other definitions for sandwich that I've seen before include "See 16" , "Golf club" , "Pieces of bread with filling" , "The snack might result in bad chin wads" , "seaside town" .)