an imperial order or decree
敕 centers on an authoritative command: an imperial order or decree, carrying the weight of official proclamation.
敕 combines 束 (bundle, to bind) with 攵 (action, strike), suggesting the binding force of an official command. The exact historical development is uncertain, but the component combination fits the idea of an authoritative decree.
The left side 束 looks like a tied bundle of official documents, and the right side 攵 is a hand holding a stick, representing authority. Together they show an imperial decree being issued with binding force.
For チョク, imagine an imperial official named Chou (pronounced 'choh') knocking a bundle of decrees with a stick: Chou -> チョク, and the knock enforces the order.