"Clairière" (from Latin clarus: "action of clearing, clearing up").
Clearing in ordinary language means something like "forest clearing" ... to clear a wood is to cut some trees in the forest, opening a clearing.
This heart center is probably the clearing itself; however, it is not an external destination, such as a distant place that one reaches after leaving one's own place of residence, but a place that has always been near, which one nevertheless glimpses only rarely and suddenly by entering the depths of the forest.
