the foot or feet, cast of a play
踋 centers on the foot or feet as a body part. The meaning 'cast of a play' is a rare, possibly archaic or specialized usage that does not clearly connect to the foot sense; treat it as a separate, context-dependent meaning.
踋 is a rare character. It combines 足 (foot) with 却, which may have contributed a sound element, but the exact historical development is uncertain.
The left side is 足 (foot), so 踋 is about the foot. Picture a foot stepping onto a stage to join the cast of a play, linking the two meanings.
For キャク, imagine a foot actor in a play who always gets a 'kyack' sound effect when they step on stage: kyack -> キャク.