One who keeps working on wrecked cabs? (4)
I believe the answer is:
scab
'one who keeps working' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'wrecked cabs?' is the wordplay.
'wrecked' indicates an anagram.
'cabs' is an anagram of 'SCAB'.
'on' acts as a link.
Can you help me to learn more?
(Other definitions for scab that I've seen before include "part of healing process" , "Rat" , "Dried surface of wound" , "Crust on wound, or a blackleg" , "Dried crust on sore" .)