He's so northern! (3)

I believe the answer is:

son

'he's' is the definition.

'so northern' is the wordplay.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'so'+'n'='SON'

(Other definitions for son that I've seen before include "Male descendant" , "A relative" , "Young boy" , "Human offspring" , "Express paper" .)

I've seen this clue in the Evening Standard.

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