Determination, perseverance (8)
I believe the answer is:
tenacity
This clue is a double definition.
'determination' is the first definition.
(I know that tenacity is a type of determination)
'perseverance' is the second definition.
(I know that perseverance can be written as tenacity)
(Other definitions for tenacity that I've seen before include "Persistence in holding on" , "Doggedly pursuing" , "Ability to stick firmly to task or position" , "Firm grasp" , "Staying power" .)