Repair glass lampshade

[bhk]

I have an small antique lamp that has 4 panels of "slag" glass; one on each side. (painted iron frame)

Originally the panels were held to the sides with iron clips. On one panel one clip is missing.

A few of the clips on other panels have been replaced with a substance that looks like wax.

Suggestions appreciated; if I am off topic please suggest the appropriate one.

bhk