Cramped Northern shaft (6)
I believe the answer is:
narrow
'cramped' is the definition.
(thesaurus)
'northern shaft' is the wordplay.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'shaft' becomes 'arrow' (I've seen this before).
'n'+'arrow'='NARROW'
(Other definitions for narrow that I've seen before include "Small-minded" , "Straight or tight" , "Constricted in width" , "Strait, tight" , "Small in breadth" .)