Row ahead -- row on river (6)
I believe the answer is:
uproar
'row' is the definition.
(I've seen this before)
'ahead row on river' is the wordplay.
'ahead' becomes 'up' (similar in meaning).
'row' becomes 'oar' (oar can mean to row with oars).
'on' is a charade indicator (letters next to each other).
'river' becomes 'r' (abbreviation for river).
'oar' after 'r' is 'roar'.
'up'+'roar'='UPROAR'
(Other definitions for uproar that I've seen before include "Loud group protest" , "Big noise" , "State of commotion, noise and confusion" , "Noisy and confused commotion" , "Outbreak of noisy and boisterous behaviour" .)