In Part I of this series (http://definitionsinsemantics.blogspot.com/2011/11/how-is-definition-different-from.html), we explored explanation defined as "bringing a mind to an understanding of a topic".
There is, however, another form of explanation, of which Aristotle said "We believe ourselves to know a thing when we are acquainted with its cause" (Posterior Analytics, II C. II para 1).
One way to provide this kind of explanation is by arguing from the cause to the effect. Traditionally this involved using syllogisms where the cause was in the major premiss and the effect was in the conclusion. E.g. All ellipses show a pattern of positions X; the orbit of Mars shows a pattern of positions X; therefore the orbit of Mars is an ellipse.
This form of explanation is very satifying, and it might seem natural to try to incorporate it into definitions. However, there are reasons not to do so. First, the above form requires putting the concept to be defined into propositions, and then putting the propositions into a syllogism (an argument). And then putting all of that into the definition. But if all this is part of the definition, and the definition is supposed to substitute for the term being defined, we would seem to end up with an infinite regression. Of course, this is always a danger when the term to be defined is in the definition, but having an argument in the definition seems to assure this as the term has to be included in the argument. At least it seems that way to me - although I cannot find any description of my opinion in the literature, and I will willingly defer to others who can prove me wrong.
Secondly, putting argument into a definition exposes the definition to much greater chance of error. The propositions may be false, and the argumentation may be invalid. And why would we put the concept into propositions and arguments before we have a completed definition - surely that is jumping the gun.
My provisional conclusion, therefore, is that causal explanations should not be placed in definitions.
BUT, there is another consideration. In modern enterprises, definitions are containers as well as content. If an explanation has to be provided, and there is nowhere else to put it, then it should be put into the definition (as container, not content). The distinction between container and content is not found (at least by me) in traditional logic. Yet it is a most important consideration. I suppose we need another blog on definition as container vs. content.
If we are forced to put a causal explanation in the definition (container) then at least get the concept defined fully (content) before any explanation is provided, so the explanation is not part of the true definition (content).