River wave, sort of catching tide finally (5)
I believe the answer is:
seine
'river' is the definition.
(Seine River is an example)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for seine that I've seen before include "Paris's river" , "Paris river" , "Second longest river in France" , "Parisian river" , "French river -- type of fishing net" .)