Book part (4)
I believe the answer is:
page
'book part' is the definition.
(I know that book has part or parts page)
This is the entire clue.
(Other definitions for page that I've seen before include "a significant bit of history?" , "Leaf of book or boy servant" , "Section of biography perhaps" , "Attendant - sheet" , "Attendant - this is on one!" .)