Book may lack his detailed version? (7)
I believe the answer is:
malachi
'book' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for malachi that I've seen before include "Biblical prophet" , "Old Testament prophet" , "8, Book 39" , "Good book" , "Part of Bible" .)