Certain tadpole (4)
I believe the answer is:
newt
'certain tadpole' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for newt that I've seen before include "Ask" , "legless for a start" , "Small tailed amphibian" , "found in pond!" , "Small, lizard-like amphibian" .)