This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
燚 is a rare character composed of four 火 (fire) elements stacked together. Its exact historical development is uncertain, but it likely originated as an intensified or decorative form of fire.
Four fires stacked together suggest an intense blaze, but the kanji has no established meaning, so treat it as a visual curiosity.
For イツ, imagine the four fires hissing and spitting: the sound 'itsu' (like 'it's hot') comes from the flames.