T-strap

[ tee-strap ]
/ ˈtiˌstræp /

noun

a strap on the upper of a shoe that extends backward from the vamp and joins with a strap that crosses the upper part of the instep, forming a T.
a shoe having such a strap.

British Dictionary definitions for t-strap

T-strap

noun

(modifier) denoting a type of woman's shoe fastened with a T-shaped strap having one part passing across the ankle and the other attached to it in the middle and lying along the length of the foot Also called: T-bar