Small ice cream or treat (5)
I believe the answer is:
scone
'treat' is the definition.
The answer and definition can be both things that one consumes for nourishment as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'small ice cream' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'ice cream' becomes 'cone' (cone can refer to an ice cream cone).
's'+'cone'='SCONE'
'or' acts as a link.
Can you help me to learn more?
(Other definitions for scone that I've seen before include "Perth's settlement" , "Savoury cake" , "in which a stone was once found?" , "Accompaniment for tea" , "A little cake" .)