Riverbank romper (5)
I believe the answer is:
otter
'riverbank romper' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for otter that I've seen before include "Torte (anag)" , "Water animal with webbed fee, brown fur and flat tail" , "Carnivorous aquatic mammal" , "Fish-eater of the weasel family" , "Fish-eating member of weasel family" .)