This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 傠 is uncertain. It visually combines 亻 (person) with 討, but the original component relationship is unclear.
The meaning is unclear, so a mnemonic is not possible. Focus on the shape: a person 亻 beside 討.
For ハツ, imagine a person 亻 discussing 討 a hat: hat -> ハツ, though the meaning remains uncertain.