a different kettle of fish

a Determinative

— A is used when the following word could be any of a certain type. Compare "A book I saw on the shelf" and "The book I gave you yesterday".

a Noun

— A is the first letter of the alphabet. The letter "a" comes before "b". — In some schools, an A is a very high grade. Ron got an A on his earth science test.

different Adjective

— If two or more things are different, they are not like each other, not the same. The two things have two sizes, not both the same size; or they have two shapes, they don't both have one shape; or they each have a color, not just one color for both things; or they are not the like each other in some other way. The day and night are quite different. My brother's bike is different from mine.

kettle Noun

— A container for boiling liquids or cooking food. William cooked the beans in a kettle. — A container for boiling water for tea; a teakettle. Stick the kettle on and we'll have a nice cup of tea. — A pothole. — The collective noun for a group of airborne hawks. — A steam locomotive — A kettledrum. — A kettle hole. — small type boiler

of Preposition

— Made using. It is a house of cards.

fish Noun

— A fish is an animal that lives in the water and has scales and gills. When I went fishing, I only caught two fish. — Fish is the meat of a fish. White wine goes well with fish.

fish Verb

— To fish means to catch fish, or to get other things that are in the water. He fished the ball out of the river.