Extremely firm concerning back-to-front convalescence (8)
I believe the answer is:
recovery
'convalescence' is the definition.
(I know that convalescence can be written as recovery)
'extremely firm concerning back-to-front' is the wordplay.
I cannot really see how this works, but
'extremely' could be 'very' (very can mean extremely or considerably) and 'very' is present in the answer.
'firm' could be 'co' (a firm is a company) and 'co' is located in the answer.
'concerning' could be 're' (both can mean on a particular topic) and 're' is found within the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for recovery that I've seen before include "A return to good health" , "A return to a normal state of health" , "Act of getting better" , "Upturn" , "Retrieval - restoration of health" .)