Joke about northern type (4)
I believe the answer is:
kind
'type' is the definition.
(I've seen this in other clues)
'joke about northern' is the wordplay.
'joke' becomes 'kid' (I've seen this before).
'about' indicates putting letters inside.
'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" .)