Unwilling to negotiate (7)
I believe the answer is:
adamant
'unwilling to negotiate' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for adamant that I've seen before include "Fully determined" , "intractable" , "Obdurate and unyielding" , "Refusing to change one's mind" , "With mind made up" .)