Pectinase (Pectic Enzyme) is an enzyme which breaks down pectin into insoluble solids that settle down to the bottom of the fermentation vessel helping to clarify the wine.

The resulting sediment can then be filtered out or you can just siphon off the clear liquid from the top, leaving the undesirable precipitates in a sludge on the bottom.

In wine-making, this is called "racking."