Evil guy popular round America (7)
I believe the answer is:
heinous
'evil' is the definition.
(similar in meaning)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for heinous that I've seen before include "Shocking (offence)" , "Very wicked, maybe in-house" , "Revolting" , "Utterly odious (crime)" , "Atrocious" .)