To cleanse a wand is to remove any energy that is not of the metal itself, it allows the energies of the metal to work freely without the interaction of other energies.
To cleanse any item there are a number of methods.
Water cleansing - where the item is placed into running spring water, to "carry" negative energies away.
Salt water cleansing - to place the item into salt water (salt is nutralising and cleansing).
Pass through incense smoke - often certain incenses like white sage are used.
Pass through smoke - often sage sticks, sage and white sage are very cleansing in energy.
Burry it - some people stick to burying items as a form of cleansing, the Earth takes back the excess energy from the item leaving it cleansed.
There are other methods so you will need to do some research into what is the best for the metal.
Some metals will react badly to being in water so please be careful.