Does he turn his master out? (5)
I believe the answer is:
valet
'his master out?' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'does he turn' is the wordplay.
'does he' becomes 'vale' (I can't justify this - if you can you should believe this answer much more).
'turn' becomes 't' (abbreviation in Oxford Dictionary of Abbreviations).
'vale'+'t'='VALET'
Can you help me to learn more?
(Other definitions for valet that I've seen before include "Personal serving man" , "Jeeves?" , "Batman" , "Personal servant" , "Clean (a car); attendant" .)