I would say that how you can tell if your speech is written clear and concise is by making sure your words aren’t misspelled, you use your grammar properly, you don’t go off topic, getting to the point of what you are taking about in a short manner and then going on to explain, make sure your audience can understand the point you are making easily, and chose wise words, get rid “that” and “there is.” Hope this helps..
The subject of the poem is life. When you look at it in depth, its entirety is a metaphor for the passing of life. Nature's first green is gold (the birth of a child, or new life), her hardest hue to hold (innocence passes fast with life, no matter how hard we try to hold on to it). Her early leaf's a flower; but only so an hour (again with the quick passing of time for life.) The leaf subsides to leaf. So Eden sank to grief (death at the end of someone's life and the mourning that comes with it, if only a second to the hour of life), so dawn goes down to day (mourning is over, and the days continue after that someone passes and everyone has mourned). Nothing gold can stay (life is valuable, like gold, and vanishes much in the same way).