Related Clues:

• Healthy capacity for vigorous activity
• Exertion of force
• It's measured in joules
• It's measured in joules or ergs
• 'Vigour, vitality (6)'
• Strength, vitality
• Can you force this to become greeny?
• Forceful enough to make Y green
• The force needed to make Y green?
• The force of a green Y?
• The way to get to the green Y by force
• can y get green with it?
• The force that could make this a green Y
• Force Y to get green and make it (6)
• The force of the green Y