poorly behaved (7)
'poorly behaved' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for bad that I've seen before include "Stinking" , "Mouldy, off" , "not healthy" , "Wicked" , "Rotten, evil" .)
(Other definitions for naughty that I've seen before include "titillating" , "Wicked" , "wayward" , "Sinful" , "Disobedient, child perhaps" .)