Guide back to the border (5)
I believe the answer is:
pilot
'guide' is the definition.
(pilot can mean a navigator)
'back to the border' is the wordplay.
'back' says the letters should be written in reverse.
'the border' becomes 'lip' (I've seen this in other clues).
'to'+'lip'='tolip'
'tolip' backwards is 'PILOT'.
(Other definitions for pilot that I've seen before include "Steer (a ship or plane)" , "One who brings a vessel into port" , "Aircraft captain" , "Plane flier" , "Guide, steer" .)