What an "anchor" supposedly does is absorb some of the scent so the fragrance is released more slowly. This means the scent will not be as intense at first, but it will theoretically last longer. I'm skeptical that it works in soap. In a powdered product, I think an anchor can be useful.
An added scent, such as the citronella or lemongrass that Dixiedragon mentioned, is not an anchor in the sense that it absorbs the fragrance. What it does do is make the overall scent last longer if you choose the right secondary scent. Fragrances can be top, heart (middle) or base notes. Top notes are the most volatile and evaporate fast. Citrus and floral scents are usually top notes. Base notes are the least volatile and last longest. They are usually wood, resin, and spice scents. Middle notes are in between and typical middle notes are the herbs and grasses. So if you are using a lemon EO (top note) and you add lemongrass to the fragrance blend, you are adding a middle note. Blending a middle note with a top note should make the overall scent last longer, mainly because the lemongrass will still be hanging around long after the lemon EO is gone.
My opinion only....