Related Clues:

• Horse's mother
• Dentist's suggestion
• Fort Peck, for one
• Obstruct
• Beaver's project
• Grand Coulee, e.g.
• Embankment
• Electricity source
• Three Gorges project
• Farm female
• It'll hold water
• One that's holding back?
• Impede
• Dentist's direction
• Part of a horse's pedigree