Northern poem makes a point (4)
I believe the answer is:
node
'a point' is the definition.
(I know that node is a type of point)
'northern poem' is the wordplay.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'poem' becomes 'ode' (ode is a type of poem).
'n'+'ode'='NODE'
'makes' is the link.
(Other definitions for node that I've seen before include "Point of intersection" , "Network junction" , "Point in network where lines intersect or branch" , "Done (anag.); a knot" , "Slight swelling on a plant where new leaves emerge" .)