Mushy peas are able to be exchanged for snacks (7)
I believe the answer is:
canapes
'mushy peas' is the definition.
The definition and answer can be both things that one consumes for nourishment as well as being plural nouns.
Maybe there's a link between them I don't understand?
'able to be exchanged for snacks' is the wordplay.
'able' becomes 'can'.
'to be exchanged for snacks' becomes 'apes' (I can't explain this - if you can you should believe this answer much more).
'can'+'apes'='CANAPES'
'are' is the link.
Can you help me to learn more?
(Other definitions for canapes that I've seen before include "for the party buffet" , "Savoury spreads on bread or toast as appetizer" , "food for party" , "Small party eats" , "Appetisers" .)