Sailor advanced westwards, getting set of maps (5)
I believe the answer is:
atlas
'set of maps' is the definition.
(book of maps)
'sailor advanced westwards' is the wordplay.
'sailor' becomes 'salt' (salt is a kind of sailor).
'advanced' becomes 'a' (abbreviation).
'westwards' says the letters should be written backwards (letters go right to left or from 'east' to 'west').
'salt'+'a'='salta'
'salta' back-to-front is 'ATLAS'.
'getting' is the link.
(Other definitions for atlas that I've seen before include "Legendary weightlifter" , "Book of maps or charts" , "Titan who supported the heavens" , "Titan with a fearsome burden" , "Mythological Titan (involved with the world of maps?)" .)