Explanation

Clearance is similar to a discovered attack or discovered check, in that you move one piece to reveal a threat of another piece. For a discovered attack or check that threat is a direct attack or check. For clearance, that threat can be checkmate, or some other tactics.

A clearing move can be especially strong if it is a forcing move, for example a capture, a check, or an attack. In that case, the opponent often cannot handle that forcing move, and the revealed threat at the same time.

In this level the revealed threat is a skewer. You move one piece out of the way for a skewer by another piece on a subsequent move.

Examples

Black can attack White's bishop with 1...c5, which also clears the way for Black's bishop to c6.
If White captures the pawn with 2.Bxc5, Black can win with 2...Bc6+, skewering White's king and rook.
Note that the counter attack 2.Rb2 does not help White because of 2...Rxd4+, or 2...Bc6+.

White can sacrifice the exchange with 1.Rxd5!
Black has to recapture with 1...cxd5.
The way for the bishop to d4 is now clear, and White can win a rook back with the skewer Bd4+.
In the end, White has won a knight and is a piece up in the endgame.

Related motifs

With clearance, you move one piece to reveal a threat of another piece.
If that threat is a direct attack, it is called discovered attack, or discovered check.

You can also combine clearance with other motifs: