Voice raised in row by Cornish river (8)
I believe the answer is:
falsetto
'voice raised' is the definition.
(I've seen this before)
'row by cornish river' is the wordplay.
'row' becomes 'setto' (I've seen this before).
'by' is a charade indicator (letters next to each other).
'cornish river' becomes 'fal' (River Fal).
'setto' after 'fal' is 'FALSETTO'.
'in' acts as a link.
(Other definitions for falsetto that I've seen before include "Unusually pitched" , "Unnaturally high-pitched voice" , "Artificially high singing voice" , "Artificially high voice pitch" , "Artificial upper register of a male voice" .)