In just three short lines, the speaker looks back on a life spent working in a mine. The first line is blunt and a little shocking: he "bled red years," as if the years themselves were his blood, drained away by the work. Time here isn't just spent, it's paid for with the body.
The second line turns the mine into something stranger than a workplace. Going down into the earth feels like travelling backward, "back and back," out of the present altogether. Underground, the ordinary day-to-day world seems to disappear.
The last line is the quietest and perhaps the saddest. While he is away, "the clock sang to my wife." Time carries on above ground and keeps her company, as if it has taken his place. The image is oddly gentle, but it suggests loneliness and distance.
The mood is heavy, wistful, and a little eerie. The speaker doesn't complain loudly; he simply states what was taken from him.