In tea, a pet brew found in a book (7)
I believe the answer is:
chapter
'a book' is the definition.
(thesaurus)
'in tea a pet brew' is the wordplay.
'in' means one lot of letters goes inside another.
'tea' becomes 'char' (I've seen this before).
'brew' indicates an anagram.
'pet' with letters rearranged gives 'pte'.
'char' going around 'pte' is 'CHAPTER'.
'found in' acts as a link.
(Other definitions for chapter that I've seen before include "Episode" , "Sequence - section of book - church body" , "series of events" , "Ecclesiastical assembly or subdivision of a written work" , "Part of book" .)