one-trick pony

Noun

Singular one-trick pony

Plural one-trick ponies

1. (countable) An animal in a performance (like a circus) who only knows how to do one trick.
   1. (idiomatic) (by extension) Someone who has only one thing that they're good at, or someone who is well-known for one thing and one thing only.
      • Synonyms: one-hit wonder and master of one