April 1 victim (4)
I believe the answer is:
'april 1 victim' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for fool that I've seen before include "Idiot" , "Dessert of pureed fruit and cream" , "Trifle" , "Ass - clown" , "Part of 1 25 [KING LEAR]" .)