Word that becomes its own synonym when the last letter is changed to "r"

BAN

Think of a short command that stops something, then tweak its ending to describe a formal gathering instead.

The word "ban" means to officially prohibit something. If you swap its last letter "n" for an "r," you get "bar," which also means to block or prevent—making it a synonym of the original word. This clue plays on the idea that a small letter change turns the word into its own near-equivalent.