One might get a stiff back cured by him (8)
I believe the answer is:
embalmer
'one might get a stiff back cured by him' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'back cured by him' is the wordplay.
'back cured' becomes 'balmer' (I am not sure about this - if you are sure you should believe this answer much more).
'by' means one lot of letters go next to another.
'him' becomes 'Em'.
'balmer' put after 'em' is 'EMBALMER'.
Can you help me to learn more?
(Other definitions for embalmer that I've seen before include "Mortician who treats corpses with preservatives" , "Person preserving a corpse" , "Mummy creator" , "One preserving bodies" , "One should preserve" .)