Edible, you can have it in cakes (4)
I believe the answer is:
fish
'edible' is the definition.
The answer and definition can be both things that one consumes for nourishment as well as being singular nouns.
Maybe there's a link between them I don't understand?
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for fish that I've seen before include "Aquatic animal" , "Angle, troll" , "Aquarium" , "Eg, sturgeon" , "Possibly the sole" .)