Rower and duck on a river (3)
I believe the answer is:
oar
'rower' is the definition.
(I've seen this before)
'duck on a river' is the wordplay.
'duck' becomes 'o' (resembles zero - 'duck' in cricket).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'river' becomes 'r' (abbreviation).
'o'+'a'+'r'='OAR'
'and' is the link.
(Other definitions for oar that I've seen before include "Rowing device" , "It ends in blade" , "Propelling blade" , "Boat propellant" , "Bladed pole" .)