Nothing to check wife leaving European city (4)

I believe the answer is:

oslo

I'm a little stuck... Click here to teach me more about this clue!

'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 Independent and The Sun.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.