His efforts have been brought to book (6)
I believe the answer is:
author
'his efforts have been brought to book' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
This is the entire clue.
Can you help me to learn more?
(Other definitions for author that I've seen before include "Creator of written work" , "Generator of written work" , "One who has written" , "He wrote the book or play" , "Generator, source" .)