Cuckoo lacking feeling? (9)
I believe the answer is:
senseless
I believe this is a double definition.
'cuckoo' is the first definition.
(both can mean insane)
'lacking feeling?' is the second definition.
(without feeling or sense)
(Other definitions for senseless that I've seen before include "Futile" , "Unconscious; stupid" , "Mindless, pointless" , "Wildly foolish" , "Illogical; stupid" .)