This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
燌 combines 火 (fire) with 賁, which likely contributes sound. The exact historical development is uncertain.
The left side is fire 火, and the right side 賁 suggests a sound. Without a clear meaning, picture a mysterious fire that is hard to name.
For フン, imagine a fun, crackling fire: fun -> フン, even though the kanji's meaning is uncertain.