Guide straight (6)
I believe the answer is:
direct
I believe this is a double definition.
'guide' is the first definition.
(I know that guide is a kind of direct)
'straight' is the second definition.
(I know that straight can be written as direct)
(Other definitions for direct that I've seen before include "Supervise; unambiguous" , "By the shortest route" , "Instruct" , "Frank; supervise" , "Guides do it" .)