Poetic Inspiration Takes Patience
The speaker refers to the loneliness of these moments twice, describing the clock as lonely as well as the darkness of the midnight forest which has sprung up in his imagination. He cannot pursue the metaphorical fox, the titular thought fox that represents poetic inspiration, or else it could flee from him and be lost within the forest. The speaker must await the fox, letting it approach him however slowly and cautiously it must, in order to benefit from its beauty.
The speaker has prepared for this moment, sitting quietly at midnight and in the darkness. He is ready for the thought fox to come, prepared for it to make itself known, and he is willing to do whatever is necessary to coax it out, to allow it to come to him "about its own business," and to endure whatever difficult or unbeautiful truths it might bring with it—its "hot stink." He must let it be what it wants to be and do what it wants to do on its own time, or else it could run away like a half-formed thought.
The Process of Writing Requires the Same Focus as Hunting
This seems to be a process that the speaker has been through before; he refers in the first line to "this" midnight's forest as though there have been many others. He returns to this forest of his imagination again and again, awaiting the inspiration brought by the thought fox. He is absolutely focused on the fox, each of the animal's movements, keeping incredibly still himself so as not to frighten the fox away. He is aware only of its presence at first, and then he sees its movement, and eventually he can even smell it. He is absolutely focused only on this animal.