Determined, unyielding (7)
I believe the answer is:
adamant
I believe this is a double definition.
'determined' is the first definition.
(I've seen this in another clue)
'unyielding' is the second definition.
(I've seen this in another clue)
(Other definitions for adamant that I've seen before include "intractable" , "Decided" , "Impervious to pleas or persuasion" , "Unyielding to requests, stubborn" , "Refusing to change one's mind" .)