Don't descend, connect
Black to play and settle the top side shape.
This situation comes from the 4-4 point, double low approach.
Arieh Question - The cutting point at a seems to completely undermine the purpose of settling the shape. I'm only a beginner, but it seems to be me that if white plays a here, black is in very bad shape, so the gote play in the previous diagram is preferable. Also, I don't think white has to play 4 immediately. White can cut at a in sente, protect the cutting stone by extending and threatening white's triangle above and then play 4.