Related Clues:

• Instant, or what you'll find in each set of circled letters
• Blue duo? (anag)
• After break, back in a jiffy
• Zagreb: largest city in Croatia -- and this instant!
• Instant ... hinted at four times in this puzzle's circled letters
• 23rd in a series ... or a hint to 27-Across
• Summer break, briefly?
• Brief moment, or what three long answers in this puzzle have?
• Ulster upset initially with leader?
• Moment that goes by quickly
• Croatian port getting support in a jiffy