Suggestion about river jaunt (4)
I believe the answer is:
trip
'jaunt' is the definition.
('trip' can be a synonym of 'jaunt')
'suggestion about river' is the wordplay.
'suggestion' becomes 'tip' (tip is a kind of suggestion).
'about' means one lot of letters goes inside another.
'river' becomes 'r'.
'tip' placed around 'r' is 'TRIP'.
(Other definitions for trip that I've seen before include "Jaunt" , "blunder" , "often occurring just before the fall" , "Short excursion" , "day out?" .)