"Just kidding!" (5)
'just kidding' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for not that I've seen before include "Word of negation" , "A negative word" , "logically, operation needed" , "Negation of what follows" , "In no way, never" .)
(Other definitions for psych that I've seen before include "Mind doctor (colloquial abbreviation)" , "Stimulate" , "To subject to mind games" , "Intimidate someone by making him feel uneasy" .)