In a Dutch oven, brown beef on all sides in oil over medium-high heat; drain. Add the cider, broth, vinegar, salt, thyme and pepper; bring to a boil. Reduce heat; cover and simmer for 1-1/4 hours.
Add the potatoes, carrots, celery and onions; return to a boil. Reduce heat; cover and simmer for 30-35 minutes or until beef and vegetables are tender.
Combine flour and water until smooth; stir into stew. Bring to a boil; cook and stir for 2 minutes or until thickened. If desired, serve with fresh thyme.
