Villain originally concealing accent (5)
I believe the answer is:
rogue
'villain' is the definition.
(rogue is a kind of villain)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for rogue that I've seen before include "Charlatan" , "Bad guy" , "Baddy" , "Stray" , "Diseased plant" .)