to pass, to step over, to creep, to twine round
躝 centers on movement that crosses or winds around: passing over, stepping across, creeping along, or twining round something.
躝 combines 足 (foot) with 闌, which likely contributes the sound and may relate to crossing or winding movement. The exact historical development is uncertain.
The foot radical 足 suggests movement, and the right side 闌 looks like a gate or barrier. Picture a foot stepping over a gate, creeping through, or twining around it.
For ラン, imagine a runner stepping over hurdles: run -> ラン, and the foot 足 carries you over each one.