Related Clues:

• First event in a series
• First game of the season
• Key, e.g.
• Game one
• First game of a doubleheader
• Curtain raiser
• One who says 'one club,' e.g.
• First in a series
• First bid
• Act before the headliner
• First of a series
• It concludes the off season
• Doubleheader half
• See 26 Across
• Cap lifter