Spotted cuckoo (5)
I believe the answer is:
dotty
I believe this clue is a double definition.
'spotted' is the first definition.
(thesaurus)
'cuckoo' is the second definition.
(thesaurus)
(Other definitions for dotty that I've seen before include "Feeble-minded" , "Bonkers; speckled" , "Eccentric, slightly mad" , "Mildly eccentric" , "Slightly crazy" .)