Joke about northern type (4)
I believe the answer is:
kind
'type' is the definition.
(I've seen this before)
'joke about northern' is the wordplay.
'joke' becomes 'kid' (I've seen this in other clues).
'about' is an insertion indicator.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'kid' enclosing 'n' is 'KIND'.
(Other definitions for kind that I've seen before include "Sympathetic" , "Gracious" , "Sort; considerate, friendly" , "Good-natured" , "Loving; class" .)