Craziness (6)
'craziness' is the definition.
(I know that craziness can be written as lunacy)
This is all the clue.
(Other definitions for lunacy that I've seen before include "Foolishness" , "Tomfoolery" , "Extreme folly, insanity" , "idiotic act" , "State of madness" .)
(Other definitions for idiocy that I've seen before include "Chopper" , "Extreme foolishness" , "Great folly" , "Foolishness, asininity" , "Stupid act" .)