Villain in clear as calculating (6)
I believe the answer is:
rascal
'villain' is the definition.
(I know that rascal is a type of villain)
'in clear as calculating' is the wordplay.
'in' indicates a hidden word.
'RASCAL' is hidden in the letters of 'clear as calculating'.
(Other definitions for rascal that I've seen before include "Mischievous person or confused lascar" , "Cheeky person, scamp" , "not one to be admired" , "Reprobate" , "Villain" .)