Hiker's aid (3)
I believe the answer is:
map
'hiker's aid' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for map that I've seen before include "Diagram of part of the earth's surface" , "Chart" , "Travel guide" , "Diagram of an area" , "Representation of earth's surface as a guide" .)