Perseveres (8)
I believe the answer is:
persists
'perseveres' is the definition.
('persist' can be a synonym of 'persevere')
This is all the clue.
(Other definitions for persists that I've seen before include "Continues firmly or obstinately" , "Is resolute" , "Perseveres in spite of opposition" , "Continues in attitude or objection" , "Continues to exist" .)