Plot over cruel torment (7)
I believe the answer is:
bedevil
'torment' is the definition.
(I know that torment can be written as bedevil)
'plot over cruel' is the wordplay.
'plot' becomes 'bed' (a plot of land).
'over' is a charade indicator (letters next to each other) (in a down clue, some letters go over others).
'cruel' becomes 'evil' (I've seen this in another clue).
'bed'+'evil'='BEDEVIL'
(Other definitions for bedevil that I've seen before include "Cause continual difficulties" , "Cause difficulties for, like Satan?" , "trouble" , "torment" , "Dog" .)