Put on the river? (3)
I believe the answer is:
don
I believe this clue is a double definition.
'put on' is the first definition.
('don' can be a synonym of 'put on')
'the river?' is the second definition.
(Don is an example)
(Other definitions for don that I've seen before include "Flower" , "Put on the learned man" , "A mafia chief or Spanish grandee" , "Put on or assume" , "Member of university" .)