long
捄 centers on the idea of length or being long. The single given meaning is narrow, and the kanji is rare, so its conceptual range is limited.
捄 combines the hand radical 扌 with 求, which may have contributed a phonetic element. The exact historical development is uncertain, and the modern form should not be over-interpreted.
The hand 扌 reaches out to measure something long, like a long piece of cloth, with the right side 求 suggesting the act of seeking its full length.
For ク, imagine a long, cool (クール) measuring tape held by the hand: cool -> ク, and the hand stretches it out to measure length.