Stamina (9)
I believe the answer is:
endurance
'stamina' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for endurance that I've seen before include "Shackleton took to the Antarctic" , "Patient toleration" , "Stoical coping with hardship" , "Crude Anne (anag.)" , "Lasting nature" .)