It is true that often people use the words smart, clever and intelligent interchangeably. In fact, I think there are notable differences between the three terms.
Smart is an individual's quality and often carries a positive connotation. It is a polysemic qualifier whose manifestation may involve a tactical or strategic act.
Clever on the other hand carries a bit of a negative connotation and I tend to associate it with engaging in an act whose outcome is mainly self-interest rather than value distribution in a wider sense. The act of being clever does not necessarily benefit others.