Bring a large saucepan of salted water to a boil. Add the farro and boil over moderately high heat until tender, about 25 minutes. Drain and cool under running water. Shake well; transfer to a large bowl.

Meanwhile, in a nonstick skillet, heat the oil. Add the pancetta and cook over moderate heat, turning once and pressing to flatten, until crispy, 6 minutes; transfer to a plate, leaving the fat in the skillet. Add the radishes, vinegar, and honey to the skillet, season with salt and pepper and simmer over low heat until the radishes are crisp-tender and glazed, 10 minutes. Stir in the lemon juice.

Scrape the radishes and dressing into the farro. Add the celery hearts, celery leaves, and goat cheese. Crumble the pancetta into the bowl and toss. Season with salt and pepper and serve.