Go over plot for one who's habitually bad-tempered (10)
I believe the answer is:
crosspatch
'one who's habitually bad-tempered' is the definition.
(bad-tempered person)
'go over plot' is the wordplay.
'go over' becomes 'cross' (to cross over).
'plot' becomes 'patch' (synonyms).
'cross'+'patch'='CROSSPATCH'
'for' acts as a link.
(Other definitions for crosspatch that I've seen before include "Ill-natured type" , "Grump" , "Ill-tempered person" , "Irascible type" , "Bad-tempered person" .)