Red nuance is about stamina (9)
I believe the answer is:
endurance
'stamina' is the definition.
(I know that stamina can be written as endurance)
'red nuance is about' is the wordplay.
'is about' indicates anagramming the letters.
'red'+'nuance'='rednuance'
'rednuance' is an anagram of 'ENDURANCE'.
(Other definitions for endurance that I've seen before include "Ability to stay a difficult course, courage" , "Ability to withstand hardship for long periods" , "ability to survive" , "Polar ship" , "Ability to withstand prolonged hardship" .)