Books sea salt order (7)
I believe the answer is:
atlases
'books' is the definition.
(I've seen this before)
'sea salt order' is the wordplay.
'order' is an anagram indicator.
'sea'+'salt'='seasalt'
'seasalt' anagrammed gives 'ATLASES'.
(Other definitions for atlases that I've seen before include "Sea-salt (anag)" , "Map books" , "Book of maps" , "navigation aids" , "Books of maps" .)