Book a useless house by the ocean (5)
I believe the answer is:
hosea
'book' is the definition.
(book of the Hebrew Bible)
'a useless house by the ocean' is the wordplay.
'a useless house' becomes 'ho' (abbreviation for house. I am not sure about the 'useless' bit.).
'by' means one lot of letters go next to another.
'the ocean' becomes 'sea' ('sea' can be a synonym of 'ocean').
'ho'+'sea'='HOSEA'
Can you help me to learn more?
(Other definitions for hosea that I've seen before include "Book of the Old Testament - a shoe (anag)" , "OT prophet" , "Book of prophecies" , "bookmaker" , "Good book" .)