Clear and concise communication results from knowing your audience
Take a look at the picture. Is it a picture of bare trees or of trees that are just about to burst into leaf?
Your interpretation depends as much on you as it does on this picture of trees in late April.
Your words are like the bare branches of these trees. When you choose them well, they burst into leaf in the minds of your listeners or readers. Just a few words can grow into a rich impression. When you choose without enough thought, your concise expression will just be bare branches.
Too often, we think that qualities like "clear" or "concise" are absolutes, qualities that are found in the writing alone. They are actually descriptions of a relationship between a communicator, an audience and a message. They define the sweet spot where the fewest words have the greatest impact because they represent shared experience and understanding.
Think of a time someone has been abrupt with you: you were given a bare branch but not enough information to imagine that branch in full bloom. Think of a time you were frustrated by someone who couldn't follow your (obviously clear) instructions. You gave them the bare branch, but perhaps they didn't know what kind of leaves to expect from it.
There is no clarity in words: there is only a finely tuned attention to meeting your audience in their experience so that they can imagine more than your words can say.