Early Primitive Elvish
alu
root. cleanse, dress
alhu
root. cleanse, dress
alnu
root. cleanse, dress
alyan-
noun. alyan-
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A root in the Qenya Lexicon of the 1910s glossed “cleanse, dress” with variants ᴱ√ALHU, ᴱ√ALNU (QL/30). For the sense “clean” there are other later roots like ᴹ√POY that may replace it (Ety/POY). The gloss “dress” seems to refer to dressing or treating material like leather, based on the derivative ᴱQ. alu “dressed leather”; there seems to be no later replacement for this other sense.