Large amphibian (8)
I believe the answer is:
bullfrog
'large amphibian' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for bullfrog that I've seen before include "Jumper" , "Large leaping amphibian" , "Creature with a deep croak" , "Amphibian with deep croak" , "Large croaker" .)