The speaker begins by dismissing a pair of lovers "on stage" with a shrug: they've seen better. It's an odd, slightly dry opening, as if romance performed for an audience has lost its power to impress. The poem then moves from that theatrical scene to somewhere quieter, "under oranges / on a summer evening," which the title suggests is an orchard. The setting feels warm, unhurried and real in a way the stage isn't.
The last lines are the trickiest. "The most ordinary touch / of vice to supper" seems to say that a small, everyday hint of wrongdoing or indulgence comes along to the meal. The word "vice" is unexpected next to something as plain as supper, and the poem doesn't explain it. Judging by the tone, the speaker feels calm and a little wry, preferring the quiet pleasure of the evening to any grand display. The mood is sensual, relaxed and gently mischievous, leaving you to decide what that touch of vice really is.