Possible Clues:

• Apt way to enter Rotary Club?
• Entrance to some office buildings
• Hotel entrance, often, and, literally, what each set of four puzzle 35-Across contains
• Metaphorical feature of a poorly run company, perhaps
• Entrance to some buildings
• Entrance of a sort, and a hint to the progression in the circles
• Energy-efficient entrance
• Hotel entrance, often
• Metaphor for high turnover
• Turning entrance