Loco, flyer (6)
I believe the answer is:
cuckoo
I believe this clue is a double definition.
'loco' is the first definition.
(I know that loco can be written as cuckoo)
'flyer' is the second definition.
(I know that cuckoo is a type of flyer)
(Other definitions for cuckoo that I've seen before include "Bird (with a bad reputation)" , "nuts" , "Cracked" , "Bird with a two-note call" , "Bananas" .)