Heads? Crazy people (4)
I believe the answer is:
nuts
I believe this is a double definition.
'heads?' is the first definition.
(I've seen this before)
'crazy people' is the second definition.
(informal term)
(Other definitions for nuts that I've seen before include "Crazy (from Brazil?)" , "Stun (anag.)" , "Stun with hard fruits" , "Crazy; food" , "Fruit - bananas!" .)