A sailor returns a set of maps (5)
I believe the answer is:
atlas
'a set of maps' is the definition.
(book of maps)
'a sailor returns' is the wordplay.
'sailor' becomes 'salt' (salt is a kind of sailor).
'returns' shows that the letters should be reversed in order.
'salt' reversed gives 'tlas'.
'a'+'tlas'='ATLAS'
(Other definitions for atlas that I've seen before include "A geog. book; N. African range" , "Book of maps - fifteenth satellite of Jupiter" , "travel book" , "Mythological Titan (involved with the world of maps?)" , "N African mountains - seemaps book" .)