Possible Clues:

• What 35-Down may do
• Primordial slime
• Escape from, uttering cries of excitement
• Hardly gush
• Flow oh so slowly
• Back where the animals are, 'e may flow along slowly
• Leach
• Mud from said river
• Trickle slowly out
• Who is unaspirated enough to sound like a little leek, by the sound of it?