The term 'slender amphibian' can be summarized by the crossword solution of 'NEWT', which is a four-letter word. Newts are a type of salamander, which are amphibians that typically have slender bodies and moist skin. They are found in many parts of the world, including Europe, North America, and parts of Asia. Newts are usually small in size, ranging from 2 to 15 inches in length. They are carnivorous, eating insects, worms, and other small animals.