Crazy for health food (4)
I believe the answer is:
nuts
I believe this is a double definition.
'crazy' is the first definition.
(thesaurus)
'health food' is the second definition.
(thesaurus)
'for' acts as a link.
(Other definitions for nuts that I've seen before include "balls" , "One eats these" , "Mad (slang)" , "Barmy (colloq)" , "Heads - fans - fruit" .)