Ache? Feel no pain, recovering altogether finally (4)
I believe the answer is:
long
'ache?' is the definition.
('long' can be a synonym of 'ache')
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for long that I've seen before include "Extensive - pine" , "extended period" , "Sustained" , "Protracted" , "to be tall" .)