Book stopping anger is good book (5)
I believe the answer is:
bible
'is good book' is the definition.
(I've seen this before)
'book stopping anger' is the wordplay.
'book' becomes 'b'.
'stopping' indicates putting letters inside (stopping can mean blocking a gap).
'anger' becomes 'bile'.
'b' going inside 'bile' is 'BIBLE'.
(Other definitions for bible that I've seen before include "The Good Book" , "It contains scriptures" , "Book for someone swearing?" , "Holy books" , "Book regarded as the ultimate authority on its subject" .)