Possible Clues:

• Forming a line
• How garden vegetables may be planted
• One right after the other
• Where eight might be found as an unbroken sequence
• Back-to-back - is this the best place to get defensive?
• Like all the pretty maids, fighting
• Successively
• One after the other having an argument
• Like metaphorical ducks, hopefully
• One after the other forming a line