Nothing to check wife leaving European city (4)

I believe the answer is:

oslo

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'european city' is the definition.
(capital of Norway)

'nothing to check wife' is the wordplay.
'nothing' becomes 'O' (O resembles 0).
'to check wife' becomes 'slo' (I can't explain this - if you can you should believe this answer much more).
'o'+'slo'='OSLO'

'leaving' acts as a link.

Can you help me to learn more?

(Other definitions for oslo that I've seen before include "Former Christiania" , "foreign port" , "It's capital in Anglos London" , "Scandinavian port" , "Nordic capital" .)

I've seen this clue in The Sun and The Independent.

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