Water ___, mammal dubbed the "cheetah of the wetlands" for its speed and stealth (5)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
shrew
(Other definitions for shrew that I've seen before include "Insectivorous mammal" , "Little mammal; a scold" , "Tamable woman?" , "Mouse-like animal or scolding woman" , "Woman who's assertive" .)