In general, it should be sufficient if you just remove all references to the previous animation mixer so the GC can do its work.
If you want to reuse an existing mixer but just cached resources for root objects, clips and actions, use the uncache*() methods of AnimationMixer. More information in the docs:
How will we remove the reference of the animation mixer object?
I am trying
animationactions[id][0]._mixer.uncacheAction(clip,.object3D(root))
I am getting this error
Cannot set properties of undefined (setting ‘_cacheIndex’ three.js) after playing the animation.