A little grub (6)
I believe the answer is:
morsel
This clue could be a double definition.
'a little' is the first definition.
The answer and definition can be both quantities as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'grub' is the second definition.
The definition and answer can be both things that one consumes for nourishment as well as being singular nouns.
Perhaps there's a link between them I don't understand?
Can you help me to learn more?
(Other definitions for morsel that I've seen before include "(Tasty) bit" , "Small mouthful of food" , "Bite to eat" , "Tasty little piece" , "A scrap or shred of food" .)