Stubbornly persistent (8)
I believe the answer is:
obdurate
'stubbornly persistent' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for obdurate that I've seen before include "Intractable" , "Stiff-necked" , "Stubbornly resistant" , "Implacable" , "hard to influence" .)