Possible Clues:

• *The place to be, informally
• Best place to be, slangily ... and, when divided in four parts, what the answers to starred clues are?
• Happening place ... or a hint to 18-, 23-, 39- and 51-Across?
• The place to be chivvying the waiters?
• Happenin' place
• *"Happenin' scene, man!"
• *'Happenin' scene, man!'
• Happening place, colloquially*
• Wife with male, more attractive in retirement, in the fashionable place to be
• The place to be