Piece of ideology in a book (3)
I believe the answer is:
log
'a book' is the definition.
(thesaurus)
'piece of ideology in' is the wordplay.
'piece of' says the answer is hidden in the clue.
'LOG' is hidden within 'ideology in'.
(Other definitions for log that I've seen before include "Written account of a voyage" , "Enter" , "Register" , "Official record; cut part of tree trunk" , "Chunk of wood" .)