Food's not all the same, young man! (5)
I believe the answer is:
salad
'same young man' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'food's not all' is the wordplay.
'food's' becomes 'salad's' (salad is a type of food).
'not all' means to remove the last letter (not all of the word).
'salads' with its final letter taken away is 'SALAD'.
'the' is the link.
Can you help me to learn more?
(Other definitions for salad that I've seen before include "one gets dressed" , "Raw vegetable dish" , "Lettuce, cucumber etc" , "rabbit food" , "See 22" .)