Related Clues:

• Insignificant part of the whole Mariana Trench? (1,4,2,3,5)
• A fall in sea level is something insignificant (1,4,2,3,5)
• Hardly any at low tide? (1,4,2,3,5)
• The end result of walking the plank doesn't amount to much (1,4,2,3,5)
• What to expect when you've finished walking the plank doesn't amount to much (1,4,2,3,5)
• Very little indeed of what some returning astronauts anticipated? (1,4,2,3,5)
• Insignificant amount (notice letters 5 to 8 in this answer)
• Insignificant amount ... or hint to this puzzle's shaded squares