Film villain has nothing on corona (4)
I believe the answer is:
halo
'corona' is the definition.
(both can mean a glowing circle)
'film villain has nothing' is the wordplay.
'film villain' becomes 'HAL' (HAL 9000, villain in 2001: A Space Odyssey).
'has' is a charade indicator (letters next to each other).
'nothing' becomes 'O' (looks like zero - 0).
'hal'+'o'='HALO'
'on' is the link.
(Other definitions for halo that I've seen before include "Imaginary circle over saint's head" , "Circle painted over saint's head" , "Saintly ring" , "Ring of light round head" , "Sign of holiness" .)