One fleeing horrible regime (6)
I believe the answer is:
emigre
'one fleeing' is the definition.
(I've seen this before)
'horrible regime' is the wordplay.
'horrible' indicates an anagram.
'regime' anagrammed gives 'EMIGRE'.
(Other definitions for emigre that I've seen before include "Person leaving to settle in another country" , "A political exile from regime" , "outcast?" , "he was driven out of the country" , "One leaving their nation" .)