A northern wally seeing Belgian city (7)

I believe the answer is:

antwerp

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'belgian city' is the definition.
(Antwerp is a city in Belgium)

'a northern wally' is the wordplay.
'a' becomes 'an'.
'northern wally' becomes 'twerp' (I can't justify this - if you can you should believe this answer much more).
'an'+'twerp'='ANTWERP'

'seeing' is the link.

Can you help me to learn more?

(Other definitions for antwerp that I've seen before include "Wrap net around this Belgian city" , "European city" , "North Belgian port" , "9/11 [OLYMPIC VENUE]" , "Busy Belgian port" .)

I've seen this clue in The Everyman puzzle in The Observer.

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