His work is supposed to be done by someone else (6)
I believe the answer is:
forger
'his work is supposed to be done by someone else' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'his work' is the wordplay.
I cannot really understand how this works, but
'work' could be 'forge' (forge is a kind of work) and 'forge' is located in the answer.
A single letter 'r' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for forger that I've seen before include "Ironworker" , "Person who makes phoney bank notes" , "Criminal who makes dud bank notes" , "Blacksmith" , "Counterfeiter" .)