Watch it. You've got one on your tail.
4 seconds sound clip from the Star Wars: Episode IV - A New Hope (1977) movie soundboard.
You can hear this line at 01:48:04 in the Blu-ray version of the movie.
Quote context
[...]
- Squad leaders, we've picked up a new group of signals.
- Enemy fighters coming your way.
- My scope's negative. I don't see anything.
- Pick up your visual scanning.
- Watch it. You've got one on your tail.
- I'm hit!
- You've picked one up! Watch it!
- He's on me tight. I can't shake him!
[...]