This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 韷 is uncertain. It combines 音 (sound) and 出 (exit), but the original semantic or phonetic role of these components is unclear.
The kanji visually combines 音 (sound) and 出 (exit). Imagine a loud noise bursting out, but since the meaning is uncertain, treat this as a shape reminder only.
For ラク, picture a rock concert where sound (音) exits (出) the speakers: rock -> ラク.