Crazy contribution to diet? (4)
I believe the answer is:
nuts
'crazy' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for nuts that I've seen before include "Edible seeds with hard shells" , "Hard-shelled fruits or seeds" , "Unbalanced" , "Got a screw loose" , "Eccentric; coal lumps" .)