Cowboy or ranger's helping on way up ravine (6)
I believe the answer is:
arroyo
'ravine' is the definition.
(type of ravine or gully)
'cowboy or ranger's helping on way up' is the wordplay.
'helping' indicates the answer is hidden within the clue (a helping or portion of the letters).
'on way up' says the letters should be written in reverse.
'oyorra' can be found hidden inside 'cowboy or rangers'.
'oyorra' back-to-front is 'ARROYO'.
(Other definitions for arroyo that I've seen before include "Dry gully; yo roar (anag.)" , "Dry watercourse" , "Rocky ravine" , "dry course" , "Dry river gully" .)