This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
懢 combines 忄 (heart/mind) with 監, which likely contributes sound. The exact historical development is uncertain.
With 忄 (heart) beside 監 (oversee), imagine a heart that oversees desires, but the exact meaning is uncertain.
For ラン, picture a heart (忄) running (ラン) wild with desire: run -> ラン.