Refusing to change one's mind (7)
I believe the answer is:
adamant
'refusing to change one's mind' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for adamant that I've seen before include "Unpersuadable" , "Unshakable (in an opinion)" , "Obdurate and unyielding" , "Insistent, inflexible" , "Impervious to pleas or persuasion" .)