It is the foot of a baboon.
More Xhosa Proverbs:
The foot has no nose.Xhosa
The shield turned the wrong way.
Xhosa
You have exposed yourself.
Xhosa
I, the adhesive grass, will stick fast to you.
Xhosa
Guluwe's two of yesterday.
Xhosa
The baldness of a head begins at the temples.
Xhosa