Maps some mountains (5)
I believe the answer is:
atlas
I believe this clue is a double definition.
'maps' is the first definition.
(printed collection of maps)
'some mountains' is the second definition.
(I've seen this before)
(Other definitions for atlas that I've seen before include "collection of charts" , "used for maps" , "Cartographer's work" , "Book of maps or charts" , "In Greek myth, a Titan made to support the heavens" .)