This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 悘 is uncertain. It visually combines 医 and 心, but the original semantic and phonetic roles are unclear.
The top 医 suggests medicine or healing, and the bottom 心 is heart/mind. Imagine a doctor's care soothing a worried heart, but remember the actual meaning is uncertain.
For イ, picture an ill heart being healed by medicine: ill -> イ, tying the top 医 to the reading.