They show places salt-filled sea is rising (7)
I believe the answer is:
atlases
'they show places' is the definition.
(books showing where places are)
'salt-filled sea is rising' is the wordplay.
'filled' indicates putting letters inside.
'is rising' is a reversal indicator (going up in a down clue).
'salt' put into 'sea' is 'sesalta'.
'sesalta' back-to-front is 'ATLASES'.
(Other definitions for atlases that I've seen before include "Collected charts" , "Sea salt (anag.)" , "Books of maps" , "Cartographical works" , "Book of maps" .)