Part of a website or a book (4)
I believe the answer is:
page
This clue is a double definition.
'part of a website' is the first definition.
(I've seen this in another clue)
'a book' is the second definition.
(thesaurus)
(Other definitions for page that I've seen before include "Boy at match" , "Section of biography perhaps" , "Youth acting as a knight's attendant" , "Leaf of book or boy servant" , "Young attendant for part of a book" .)