Wicked mansion in Middleton, America (10)
I believe the answer is:
villainous
'wicked' is the definition.
(similar in meaning)
'mansion in middleton america' is the wordplay.
I cannot quite see how this works, but
'in' is present in the answer.
'america' could be 'us' (United States) and 'us' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for villainous that I've seen before include "really bad" , "criminal" , "very unpleasant" , "dramatically bad" , "Nasty" .)