Notice over embassy entrance (9)
I believe the answer is:
admission
'entrance' is the definition.
(admission is a kind of entrance)
'notice over embassy' is the wordplay.
'notice' becomes 'ad'.
'over' is a charade indicator (letters next to each other).
'embassy' becomes 'mission' (I've seen this before).
'ad'+'mission'='ADMISSION'
(Other definitions for admission that I've seen before include "Acknowledgment of the truth of something" , "Access" , "A confessing" , "Right to go in" , "concession" .)