Stubborn sort (4)
I believe the answer is:
cuss
'stubborn sort' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for cuss that I've seen before include "Use bad language (informal)" , "Blaspheme" , "Stubborn person" , "Oath; (annoying sort of) person" , "Swear (slang)" .)