High pitched river conflict (8)
I believe the answer is:
falsetto
'high pitched' is the definition.
(thesaurus)
'river conflict' is the wordplay.
'river' becomes 'fal' (I've seen this before).
'conflict' becomes 'setto' (set-to is a kind of conflict**).
'fal'+'setto'='FALSETTO'
(Other definitions for falsetto that I've seen before include "it sounds high" , "Voice pitch higher than the normal range" , "Unusually pitched" , "Voice one's raised" , "high notes?" .)