Naughtiness (12)
'naughtiness' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for mischief that I've seen before include "bad behaviour" , "Shenanigans" , "Black . . . . . . . . (Evelyn Waugh)" , "nuisance" , "Source of trouble" .)
(Other definitions for hanky-panky that I've seen before include "Naughty goings-on" , "Skulduggery" , "Illicit slap and tickle" , "Monkey business" , "Naughty fun" .)
'naughtiness' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for misbehaviour that I've seen before include "Bad conduct" , "Naughtiness" .)