Traitor angered English terribly (8)
I believe the answer is:
renegade
'traitor' is the definition.
(I know that renegade is a type of traitor)
'angered english terribly' is the wordplay.
'english' becomes 'E' (abbreviation).
'terribly' is an anagram indicator.
'angered'+'e'='angerede'
'angerede' anagrammed gives 'RENEGADE'.
(Other definitions for renegade that I've seen before include "Treacherous deserter" , "Dare Gene to become a rebel" , "Turncoat, rebel" , "Traitor" , "Rebel deserter" .)