Ill-natured (4)
'ill-natured' is the definition.
(similar in meaning)
This is all the clue.
(Other definitions for cantankerous that I've seen before include "Contrary and quarrelsome" , "can be prickly, too!" , "Cussed, quarrelsome" , "Crabby" , "Bloody-minded -- non-UK car seat (anag)" .)
'ill-natured' is the definition.
(similar in meaning)
This is all the clue.
(Other definitions for sour that I've seen before include "Acid-tasting" , "Acid or caustic" , "Rancid or tart" , "Curdled" , "Bitter, tart" .)