Grumpy (12)
'grumpy' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for cantankerous that I've seen before include "Stubbornly obstructive" , "Bloody-minded -- non-UK car seat (anag)" , "Cross" , "Irritable" , "Irascible" .)
(Another definition for in high dudgeon that I've seen is " Feeling resentful".)