This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 憄 is uncertain. It visually combines 徝 (top) and 心 (bottom), but the original semantic and phonetic roles are unclear.
The character has 心 (heart) at the bottom, suggesting an emotion or mental state, but the top component 徝 is obscure. Without a clear meaning, it is hard to form a reliable mnemonic.
For チ, imagine a tiny heart (心) at the bottom of the character, and think of a 'chee' sound as a small heartbeat: chee -> チ.