Fathead's food? (4)

I believe the answer is:

fool

I'm a little stuck... Click here to teach me more about this clue!

But I can't explain it at all! Could you help me understand?

(Other definitions for fool that I've seen before include "Jester - dessert" , "Deceive" , "Dessert of pureed fruit and cream" , "Jester or silly ass" , "Ass - clown" .)

Want a hint initially instead of a full solution? Install my app