He forms characters and puts them in books (6)
I believe the answer is:
writer
'he forms characters and puts them in books' 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 writer that I've seen before include "Scribe, author" , "See 1, 12, 15, 23 across and 3, 6, 9 down" , "Author; correspondent" , "Quiller" , "Pope, for example" .)