This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
粠 combines 米 (rice) with 共, but the exact historical development and original meaning are uncertain. It may have been a specialized character for a type of rice or grain product.
With 米 (rice) and 共 (together), imagine rice grains sticking together into a sticky mass, but remember that the actual meaning is unclear.
For コウ, picture a sticky rice cake that is so hard it goes 'kou' when tapped: kou -> コウ.