The answers to the clues below are in the form of common abbreviations.

1. Their spy outfit and ours
2. You'll let me know if you're coming, right?
3. Just so you know, I need it tomorrow.
4. That's it, for example
5. Alien visitors and their transport
6. He deserted, as you can see.

Answers:

1. KGB, CIA
2. RSVP, OK ? 
3. FYI, ASAP
4. i.e. , e.g.
5. ET's, UFO's 
6. AWOL, QED

Credit: LA Times Crossword
Sylvia Bursztyn and Barry Tunick
TAKE ABBREV'ER  (adapted)