Aesop cooked up dish (3,4)
I believe the answer is:
pea soup
'dish' is the definition.
(pea soup is a kind of dish)
'aesop cooked up' is the wordplay.
'cooked' is an anagram indicator.
'aesop' anagrammed gives 'peaso'.
'peaso'+'up'='PEA-SOUP'
(Other definitions for pea soup that I've seen before include "Liquid vegetable-based dish (like thick fog)" , "Dish like old London fog" , "Hot dish (like a fog?)" , "Pulse-based broth" , "starter course?" .)