Crazy? Oh no! (4)
I believe the answer is:
nuts
I believe this clue is a double definition.
'crazy?' is the first definition.
(nuts can informally mean crazy or mad)
'oh no' is the second definition.
(interjections with similar meaning)
(Other definitions for nuts that I've seen before include "Unbalanced" , "Heads - fans - fruit" , "One eats these" , "Eg, filberts, hazels" , "Bonkers" .)