the coast is clear

idiomatic

(idiomatic) There is no danger; one can freely pass through a region without risk of discovery.

Japanese Meaning

周囲に危険がなく、自由に行動できる状態 / 発覚や追及の心配がなく、安心して動ける状況 / 偵察や警戒すべき障害がなく、安全な状況

Hold on until the coast is clear, then we'll cross the courtyard.

危険がなくなるまで待ってから、中庭を渡りましょう。

Sense（1）

(idiomatic) There is no danger; one can freely pass through a region without risk of discovery.

Wait there, watch the back of the building, and whistle when the coast is clear.