Dogged, unyielding (9)
I believe the answer is:
tenacious
This clue is a double definition.
'dogged' is the first definition.
(synonyms)
'unyielding' is the second definition.
(synonyms)
(Other definitions for tenacious that I've seen before include "Holding fast" , "Persevering" , "Holding or sticking firmly" , "Keeping a firm hold" , "Determined" .)