The Indus Dictionary Project
This ideograph is composed of a track, with an arrow noticeably above the mid-point of the track. The arrow is pointing away from you. Hence, this symbol is the preposition to.
Harappa: Seal: H-141 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 200: Collections in India: Suomalainen Tiedeakatemia.
This is Mahadevan's sign number 1006, which I have redrawn to better reflect the original.
Preposition To: Lynn Fawcett, 2018.