Pond swimmer (4)
I believe the answer is:
newt
'pond swimmer' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for newt that I've seen before include "Small often colourful salamander of the Northern Hemisphere" , "Went to find kind of water lizard" , "Small, lizard-like amphibian" , "Amphibian - a Ken Livingstone pet?" , "The epitome of drunkenness" .)