The speaker feels out of place in settled, respectable life. The poem opens with a small clash: something harmful comes from a "horrid rose," a flower we usually link with beauty and romance, so the pleasant surface turns out to sting. The speaker then admits to an "ordinary lordship," a kind of everyday authority or polite society, that they come "from sea." The sea suggests something wilder and less fixed than the world they are addressing.
The middle lines make the conflict plain. A "staid home," dull and steady, would "ruin" their sleep, so comfort doesn't bring rest. Yet the final lines suggest the speaker can't simply leave either: "I cannot live partly out / and partly in." They want to belong fully to one world or the other.
The mood is restless and tense but also honest. The short lines and plain confession give it the feel of someone finally saying something hard out loud. The title, "Undercover," hints at a life lived in disguise, which the speaker is tired of.