Have you ever been working in terminal, made a typo on a commanded, hit return and got stuck? It’s ok it happens to everyone. If you are running Ubuntu, or really for most terminals and Linux based operating systems simply type ctrl+c to clear your entry.
Quick Answer
CTRL+C
By entering ctrl+c it will clear your current line and create a new command line.
Other Commands
reset
man reset
Look up the reset and man rest commands to learn more about this operation.