Snack is small in part (7)
I believe the answer is:
rissole
'snack' is the definition.
The definition and answer can be both things that one consumes for nourishment as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'is small in part' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'in' indicates putting letters inside.
'part' becomes 'role' (eg a theatrical role).
'is'+'s'='iss'
'iss' placed within 'role' is 'RISSOLE'.
Can you help me to learn more?
(Other definitions for rissole that I've seen before include "Fried ball of minced food" , "Fried meat dish" , "Minced meat or fish deep fried in egg and breadcrumbs" , "Meatball fried in crumbs" , "Meat product" .)