Does he cater for gamblers in volume production? (9)
I believe the answer is:
bookmaker
'does he cater for gamblers' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'volume production?' is the wordplay.
'volume' becomes 'book' (synonyms).
'production?' becomes 'maker' (I can't justify this - if you can you should believe this answer much more).
'book'+'maker'='BOOKMAKER'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for bookmaker that I've seen before include "One who takes bets" , "One taking bets" , "author?" , "One financially dependent on backers" , "Compiler" .)