Solutions A period of seven days has 8 entries with similar clues

• 6-letter words
• a-weekPer seven days
• weeklyPublication appearing only once in seven days
• 8-letter words
• heptagonA plane figure with seven straight sides and seven angles
• weeklongLast seven days
• februaryPeriod of twenty-eight or twenty-nine days
• 9-letter words
• triweeklyThree times in seven days
• 10-letter words
• lunar-yearPeriod of 354.3671 days
• 11-letter words
• lunar-monthPeriod of twenty-eight days