The title sets up a world of negotiation, and the poem quickly shows that the "business" here is probably a clandestine meeting between two people. The opening question, about ambassadors who "will not have a treaty with time," suggests that these two refuse to accept any agreement with the clock. They want to steal a moment, even "one day only," in a small, hidden space.
The settings get more cramped and underground as the poem goes on: a closet, a wine cellar, a pit. Each is private and a little shameful, a place away from daylight. Pleasant talk gives way to business, and business gives way to a kiss. The final image is the strangest. They kiss "like people of ice," which could mean coldness, restraint, or the stiff formality of diplomats who cannot let themselves melt.
The mood is guarded and tense, with a thread of longing underneath. The speaker seems to feel both desire and the pressure of keeping it contained, as if even intimacy has to be handled with official politeness.