Turncoat angered volatile European (8)
I believe the answer is:
renegade
'turncoat' is the definition.
(I know that turncoat can be written as renegade)
'angered volatile european' is the wordplay.
'volatile' is an anagram indicator.
'european' becomes 'E' (abbreviation e.g. EU).
'angered' is an anagram of 'renegad'.
'renegad'+'e'='RENEGADE'
(Other definitions for renegade that I've seen before include "Rebel deserter" , "Perfidious" , "not someone true to the cause" , "One who deserts a cause or group" , "Disloyal - defector" .)