Scout's rider (5)
I believe the answer is:
tonto
'scout's rider' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tonto that I've seen before include "Western companion" , "Faithful companion" , "Lone Ranger and - -" , "The Lone Ranger's companion" , "Lone Ranger's scout" .)