Poultry food is not worth much (11)
I believe the answer is:
chickenfeed
'not worth much' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'poultry food' is the wordplay.
'poultry' becomes 'chicken' (chicken is a kind of poultry).
'food' becomes 'feed' (feed is a kind of food).
'chicken'+'feed'='CHICKENFEED'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for chickenfeed that I've seen before include "very little money" , "Small potatoes" , "Not much money - for the birds" , "mash, perhaps?" , "Very small amount of money" .)