Loud noise from river paddle (4)
I believe the answer is:
roar
'loud noise' is the definition.
(I've seen this before)
'river paddle' is the wordplay.
'river' becomes 'r' (abbreviation for river).
'paddle' becomes 'oar' (I've seen this before).
'r'+'oar'='ROAR'
'from' acts as a link.
(Other definitions for roar that I've seen before include "The __ of the Greasepaint -- The Smell of the Crowd (1964 musical)" , "Deep-throated cry" , "Loud cry" , "24 [BOOM]" , "Jaguar, for example, emits this" .)