I'd say that smart was: quick to comprehend, with an implication of sassiness or newness to it. I'd define clever as witty, with overtones of foxiness and an implication that rule bending might be allowable.

All those words have to do with how much good stuff there is in the Central Processing Unit, but some have more to do with RAM than mother board, and others more to do with software . . .

It's nice to be able to pop in, thanks, bel! You're right about English. Some of us treat it as Humpty Dumpty does in Alice. Lack of shared references can keep two people who share the same language from communicating well, can't it?