For wild apes, there's nothing better to eat (3,4)
I believe the answer is:
pea soup
'for wild' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'apes there's nothing better to eat' is the wordplay.
'there's nothing' becomes 'o' (I've seen this in other clues).
'better' indicates an anagram (with an improved letter-order).
'to eat' becomes 'up' (I can't explain this - if you can you should give a lot more credence to this answer).
'apes'+'o'='apeso'
'apeso' anagrammed gives 'peaso'.
'peaso'+'up'='PEA-SOUP'
Can you help me to learn more?
(Other definitions for pea soup that I've seen before include "starter course?" , "Food - thick yellow fog" , "Dish like old London fog" , "Thick vegetable broth" , "Green potage" .)