Related Clues:
- Maze entrance word
- "Boo!" reaction
- First square of some board games
- Manual opener
- Sudden movement
- Start of an itinerary
- Making sure you have all the parts, e.g.
- Start of a plan
- One maze terminal...
- Be part of the opening lineup
- Word next to an arrow, maybe
- Possible result of a gunshot
- Boot up
- With 21-Across, begin from scratch
- Outset