Notice placed above embassy entrance (9)

I believe the answer is:

admission

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'entrance' is the definition.
(admission is a kind of entrance)

'notice placed above embassy' is the wordplay.
'notice' becomes 'ad' (both can mean an advertisement).
'placed above embassy' becomes 'mission' (I am not sure about this - if you are sure you should believe this answer much more).
'ad'+'mission'='ADMISSION'

Can you help me to learn more?

(Other definitions for admission that I've seen before include "concession" , "The price of entry" , "A confessing" , "Access" , "guilty revelation" .)

I've seen this clue in The Telegraph.

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