I'm certain Clarkson wasn't calling him stupid, as May pointed out that the nature of electricity is incredibly tricky outside of the normal usage context. In fact, I'm sure Clarkson was throwing him a veiled compliment.
"What is "electricity?" Under the scientists' definition there is a simple answer to this question: Matter is mainly composed of particles of electricity (of electrons and protons,) so if we should say that electricity is a type of matter, we wouldn't be too wrong. Electricity is not matter in the everyday sense, instead electricity is one step down from matter. It's one of the main components of matter. Electricity has mass, although for electrons the mass per cubic volume is very small (the electrons of a wire are thousands of times lighter than the copper atoms, yet the number of electrons rivals the number of atoms. "
And that's the simple definition!
(Sorry, first post, so can't post the link to the quote, but a Google search for - electricity science definition - would take you to it)