Clarifying is doing a more intense wash than usual, to remove any buildup from products or hard water.
I'm not sure about "natural" things that clarify.
My usual suggestion for clarifying is to wash with a shampoo that contains ALS (aluminum lauryl sulfide), as it cleanses thoroughly and rinses verly cleanly. TreSemme Vit. C is good. You want a shampoo that is detergent and not much else.
If you have hard water, you may want to follow with a chelating shampoo or treatment, to remove mineral buildup.
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