Aim's tan: perhaps endurance needed! (7)
I believe the answer is:
stamina
'endurance needed' is the definition.
I can't tell whether this defines the answer.
'aim's tan perhaps' is the wordplay.
'perhaps' indicates anagramming the letters.
'aims'+'tan'='aimstan'
'aimstan' anagrammed gives 'STAMINA'.
Can you help me to learn more?
(Other definitions for stamina that I've seen before include "Ability for sustained effort" , "Resilience" , "Endurance, strength to stay the course" , "Staying-power, endurance" , "Indefatigability" .)