A brute, a cur - horrible official! (10)
I believe the answer is:
bureaucrat
'official' is the definition.
(bureaucrat is a kind of official)
'a brute a cur horrible' is the wordplay.
'horrible' is an anagram indicator.
'a'+'brute'+'a'+'cur'='abruteacur'
'abruteacur' anagrammed gives 'BUREAUCRAT'.
(Other definitions for bureaucrat that I've seen before include "Administrator" , "Mandarin" , "Government official" .)