This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 敇 is uncertain. It visually combines 朿 and 攵, but the original semantic and phonetic roles are unclear.
With no clear meaning, picture the left side 朿 as a thorny plant and the right side 攵 as a hand holding a stick, perhaps poking or prodding, but treat the meaning as unknown.
For サク, imagine a sack (サク) being prodded by the stick on the right, though the kanji's meaning is uncertain.