He has a stable job (6)
I believe the answer is:
ostler
This clue could be a double definition.
'he' is the first definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'a stable job' is the second definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'has' acts as a link.
Can you help me to learn more?
(Other definitions for ostler that I've seen before include "He held the horse at the old inn" , "Nags for me" , "Inn stableman (hist.)" , "Horseman at the inn of old" , "Horse minder" .)