Greek ambassador repulsed European girl (7)
I believe the answer is:
hellene
'greek' is the definition.
('Hellene' can be a synonym of 'greek')
'ambassador repulsed european girl' is the wordplay.
'ambassador' becomes 'he' (His or Her Excellency).
'repulsed' shows that the letters should be reversed in order.
'european' becomes 'e' (abbreviation e.g. EU).
'girl' becomes 'nell' (I've seen this before**).
'e'+'nell'='enell'
'enell' in reverse letter order is 'llene'.
'he'+'llene'='HELLENE'
(Other definitions for hellene that I've seen before include "Greek girl" , "old Greek" .)