Desert gully (6)
I believe the answer is:
arroyo
'desert gully' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for arroyo that I've seen before include "dry course" , "Often dry desert ravine" , "Rocky ravine" , "Dry gully; yo roar (anag.)" , "Dry watercourse" .)