Socks on top of a book (5)
I believe the answer is:
hosea
'book' is the definition.
(book of the Hebrew Bible)
'socks on top of a' is the wordplay.
'socks' becomes 'hose' (I've seen this before).
'on top of' means one lot of letters go next to another.
'hose'+'a'='HOSEA'
(Other definitions for hosea that I've seen before include "Book of prophecies" , "Book writer" , "bookmaker" , "OT prophet/book" , "Book of the Old Testament - a shoe (anag)" .)