This symbol begins on the right with the arms element from the noun span. On the left is a pack or bundle with protruding threads. A bundle consisting of a span of threads is an ideograph for a
hank or skein of yarn.
Illustrative Text Reference:
Mohenjo-daro: Seal: M-624 a: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 5: Collections in Pakistan: Suomalainen Tiedeakatemia.
This is Mahadevan's sign number 1015, which I have redrawn to better reflect the original.