girl Scouts, Boy Scouts, cops and agents all have this one item in common. What am I?

A ring of water, guarding the castle, Protecting the throne, be it lord or vassal. A liquid hug around old towers, Keeping enemies at bay for hours.

I prefer vinyl, but there's something that sticks to me when I listen to cassettes... maybe it's because of this:

In the kitchen, I hold a spot, Where bubbling brews get quite hot. With a handle to grip, I never let slip. A cauldron's cousin, though I'm not.

In fields where flowers kiss the breeze, I dance with the whispers of ancient trees. With arms of wood, I spin my tale, harnessing the breath of Gaia's sail.