Possible Clues:

• Like 5:00 or 6:00 a.m., say
• Ahead of one's time
• Pioneering
• Lustrous, apart from first thing in the morning?
• Before expected
• Opening like St. Peter's gates, but less quietly
• When an eager date arrives
• Rely on revision to secure top mark soon
• Noble, perhaps, before one's time
• Like king or queen in Bow, head off in good time