This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development is uncertain. The modern form combines 亻 (person) with 宛, but the original semantic and phonetic roles are unclear.
A person 亻 beside 宛, a shape that appears in many characters. Without a clear meaning, picture a person standing next to a curved, roofed structure, perhaps enjoying the view.
For エン, imagine a person leaning against the 宛 structure, saying 'en' as they relax: en -> エン.