Clean這個單字相對容易瞭解，意指乾淨不受污染之意。應用在占星學上是指一顆行星沒有與凶星（malefic）聚集（assembly）或形成四分相（Square）、對分相（opposition），但也可能指沒有與凶星形成任何的相位（aspect）。亦即行星本身不受任何的凶星來影響其良好的本質，行星自然能充份發揮其正面的力量。一般在古典文獻中是以be cleansed of 的片語呈現，以下為運用的實例：
And if you wished to partner with someone in assets or in a work, it is better for this that the Moon be cleansed of the bad ones and joined to fortunes, and that she be in common signs (so that it would be multiplied), or the Moon should be in Leo or in Taurus.
But if it were in Virgo, with the Moon being mixed with Mars [and] the benevolents being turned away from the view of the sign of the eclipse, they harm the regions of Virgo with the burden of famine, unless Mercury would be cleansed of the infortunes [and] is aspecting Jupiter: and if it were like that, there is a good condition after the corruption (and it corrupts the essence which belongs to Virgo).
And for a report in which the book and letter comes, look at the Sun and Moon in their course: for if they were cleansed of the infortunes, and the Moon was with Mercury in one of those signs which we described were cleansed of the infortunes, and the fortunes are in them or looking at them, then there will be joy and delight in the book, report, and letter which reached the owner of that nativity at that hour.
