A crazy seed-case? (3)
I believe the answer is:
nut
This clue is a triple definition!
'a crazy' is the first definition.
(I've seen this before)
'seed' is the second definition.
(nut is a kind of seed)
'case?' is the third definition.
(thesaurus)
(Other definitions for nut that I've seen before include "Bolt's partner" , "Hard dry fruit - enthusiast" , "Hard-skinned fruit" , "Freak" , "One securing bolt" .)