Tolerance, with Cobalt correctly counterbalanced (9)
I believe the answer is:
endurance
'tolerance' is the definition.
(thesaurus)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for endurance that I've seen before include "Stoical attitude" , "Shackleton took to the Antarctic" , "Lasting nature" , "Bearing" , "Polar ship" .)