Does he hunt for customers? (6)
I believe the answer is:
hawker
'does he' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'hunt for customers?' is the wordplay.
'hunt' becomes 'hawk' (hawking is a kind of hunting).
'for customers?' becomes 'er' (I can't justify this - if you can you should give a lot more credence to this answer).
'hawk'+'er'='HAWKER'
Can you help me to learn more?
(Other definitions for hawker that I've seen before include "Pedlar" , "One who sells from door to door" , "Person who carries goods about for sale" , "Street-seller" , "He sells from door-to-door" .)