Indicatory anagram book (10)
I believe the answer is:
dictionary
'book' is the definition.
(I know that dictionary is a type of book)
'indicatory anagram' is the wordplay.
'anagram' indicates an anagram.
'indicatory' is an anagram of 'DICTIONARY'.
(Other definitions for dictionary that I've seen before include "Brewer's creation, say" , "Where to find the meaning of life, for example!" , "Ordered book" , "Lexicon" , "reference work" .)