We hear it's a spinach-guzzler's beloved foodstuff (5,3)
I believe the answer is:
olive oil
'foodstuff' is the definition.
The answer and definition can be both things that one consumes for nourishment as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for olive oil that I've seen before include "Ingredient of vinaigrette" , "Pressed cooking ingredient" , "Culinary liquid" , "Light yellow dressing pressed from Mediterranean tree fruits" , "Liquid used in cookery or salad dressings" .)