Some villain's not well (3)
I believe the answer is:
ill
'not well' is the definition.
('ill' is the opposite to 'well')
'some villain's' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'ILL' is hidden within 'villains'.
(Other definitions for ill that I've seen before include "Wicked" , "state, briefly" , "Sickly" , "Indisposed" , "Afflicted" .)