A climber spotted near river valley (6)
I believe the answer is:
ravine
'valley' is the definition.
(ravine is a kind of valley)
'a climber spotted near river' is the wordplay.
'climber' becomes 'vine'.
'spotted near' means one lot of letters go next to another (I've seen this in other clues).
'river' becomes 'r'.
'a'+'vine'='avine'
'avine' after 'r' is 'RAVINE'.
(Other definitions for ravine that I've seen before include "Vainer in narrow gorge" , "Steep-sided gorge" , "Narrow, steep-sided valley" , "Defile" , "Type of gorge" .)