NY Times Crossword
Kiran S. Kedlaya (adapted)

The answers to the clues below will have something in common:

1. Lights, gates and bells site, briefly
2. It indicates what's happening, briefly
3. Start playing (music), briefly
4. Popular two-wheeler, briefly

Answers:

1. RR XING
2. SIGN OF THE X
3. X UP THE BAND
4. X-SPEED BIKE