Mean northern cardinal blocks passport for one (6)
I believe the answer is:
intend
'mean' is the definition.
(to intend to something is to mean it)
'northern cardinal blocks passport for one' is the wordplay.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'cardinal' becomes 'ten' (similar in meaning).
'blocks' means one lot of letters goes inside another (the inside letters form a 'blockage').
'passport for one' becomes 'ID' (a passport is identification).
'n'+'ten'='nten'
'nten' going inside 'id' is 'INTEND'.
(Other definitions for intend that I've seen before include "Mean; propose" , "Mean; aim" , "Have as one's plan" , "Have as purpose or resolve" , "Aim, plan" .)