Exclusion of head of Omani embassy (8)
I believe the answer is:
omission
'exclusion' is the definition.
(I've seen this before)
'head of omani embassy' is the wordplay.
'head of' says to take the initial letters.
'embassy' becomes 'mission' (I've seen this in other clues).
The first letter of 'omani' is 'o'.
'o'+'mission'='OMISSION'
'of' is the link.
(Other definitions for omission that I've seen before include "Lack" , "Something lacking" , "Oversight, piece of work neglected" , "Exclusion" , "Gap" .)