The caption at the Guimet identifies this as a rat trap, one of two similar ones found at the site. The sliding door on the left would have let a rat or perhaps another creature like a mouse in.
MADE PERHAPS TO AMUSE LITTLE PREHISTORIC PEOPLE IN THE INDUS VALLEY TWO OR THREE THOUSAND YEARS AGO: TERRA-COTTA ANIMALS, BIRDS, AND OTHER TOYS FROM MOHENJO-DARO.
Published in ARASI 1924-25, Plate XXVI (a). Title: ‘Harappa: Mound B, A large collection of animals’ bones’.
From “large trench excavated in mound B … behind the Naugaza tomb”, stratum below stratum III, and the collection numbered B. 954 [ARASI