One who goes to work on foot (11)
I believe the answer is:
chiropodist
'one who goes to work on foot' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'one who goes to work' is the wordplay.
I cannot really see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
'work' could be 'op' (short for opus) and 'op' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for chiropodist that I've seen before include "One treating the feet" , "Foot specialist" , "Treater of feet" , "Treater of minor foot ailments" , "Podiatrist" .)