This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 昢 is uncertain. It visually combines 日 (sun) and 出 (exit), but the original meaning and component relationship are unclear.
The sun 日 and the shape for exit 出 together suggest the sun coming out, which could hint at dawn or daybreak, but the actual meaning is not confirmed.
For ホツ, imagine the sun popping out with a hot burst of light: hot -> ホツ, as the sun exits the horizon.