• uranium oxide (yellowcake) powder clad in zirconium metal cans
• uranium metal slug clad in zirconium metal cans
• uranium metal rods clad with stainless steel metal
• MOX (mixed uranium and plutonium oxide) powder clad in zirconium metal cans
• plutonium oxide powder clad in zirconium metal cans
• plutonium metal slug clad in zirconium metal cans
• uranyl sulfate or uranyl nitrate solution in water (fuel/moderator/coolant mixed) - primary coolant loop circulates fuel and coolant, needs 3 coolant loops, but changing fuel is almost trivial compared to other reactors
• uranium oxide (yellowcake) ceramic pellet clad in ceramic clad in pyrolytic graphite - fuel/moderator for pebble bed gas cooled inherently thermally safe reactor
• etc.
• etc.

Clad is a term used to describe coins that are not made of precious metals.

When you hear of a clad coin, it is to say it is plain junk metal, and only plated with a very thin layer of gold.

Copper-nickel clad "sandwich" metal, the same as dimes and quarters.

Yes, but often with oak, not metal.

A substation that is smaller than the average substation. A substation converts electric power from one voltage to another.