Literal translation
the stone goes to the pile of stones
Meaning
money flows to those who already have it
Explanation
Means that money goes to the rich, or more broadly that like joins like. A clapié is a pile of flat stones, clapo, that farmers cleared from the stony soil to make it fit for planting and stacked at the field's edge, a task so constant and gruelling that the image took hold in people's minds. The financial sense is by far the more common of the two.