Crazy flutters (4)
I believe the answer is:
bats
I believe this is a double definition.
'crazy' is the first definition.
(thesaurus)
'flutters' is the second definition.
('bat' can be a synonym of 'flutter')
(Other definitions for bats that I've seen before include "out to lunch" , "Those striking" , "Cuckoo" , "Crazy; night-fliers" , "Lunatic" .)