Joan, or possibly Shannon Tweed (6)
I believe the answer is:
rivers
I'm afraid I can't explain this answer.
Can you help me to learn more?
(Other definitions for rivers that I've seen before include "Comedienne Joan" , "''Only Our ... Run Free'' (MacConnell ballad)" , "''Only Our ... Run Free'' (McConnell ballad)" , "Thames and Hudson?" , "Large natural streams of water" .)