Villain takes short time in study (5)
I believe the answer is:
demon
'villain' is the definition.
(both can mean an evil person)
'short time in study' is the wordplay.
'short time' becomes 'mo' (as in 'just a mo').
'in' means one lot of letters goes inside another.
'study' becomes 'den' (term for a study or office).
'mo' inserted inside 'den' is 'DEMON'.
'takes' acts as a link.
(Other definitions for demon that I've seen before include "beast" , "Inspiring force" , "Evildoer" , "malignant spirit" , "Ghoul" .)