Book a sailor brought back (5)
I believe the answer is:
atlas
'book' is the definition.
(atlas is a kind of book)
'a sailor brought back' is the wordplay.
'sailor' becomes 'salt' (salt is a kind of sailor).
'brought back' shows that the letters should be reversed in order.
'salt' backwards is 'tlas'.
'a'+'tlas'='ATLAS'
(Other definitions for atlas that I've seen before include "Giant" , "travel book" , "Album of maps" , "I carry a huge weight" , "used for maps" .)