Possible Clues:

• Prey for a heron
• Eye of ___ (witches' ingredient)
• Eye of ___ (part of a witch's brew)
• Its eye is in many a witch's brew
• Semiaquatic creature
• Creature wife caught in trap
• An eft is a young one
• Creek critter
• Seventh-year exam in Harry Potter
• Amphibian’s leg removed by famous scientist