Related Clues:
- BACKUP
- Sub
- Take turns
- Deputy
- Stand-in
- What black and white squares do on a chessboard
- Do this, then that, then this again
- Happen in turns, rotate
- Change to first the one, then the other
- Change by turns
- First the one, then the other
- Every second one
- Happening or following in turns, one after the other
- Every second one of a series
- Interchange