If you have 6 hours or a half day to spend in Leeds, here are some suggestions:
1. Visit the Royal Armouries Museum - This museum houses a collection of arms and armor from across the world. You can see weapons and suits of armor from different time periods. It will take around 2 hours to visit.
2. Explore the Leeds Art Gallery - The gallery covers British art from the 19th century to contemporary works. You can see the works of famous artists, such as Henry Moore and Barbara Hepworth. It will take around 1-2 hours to visit.
3. Walk around Roundhay Park - It is a beautiful park with a lake, woodlands, and gardens. You can walk and relax around the park. It will take around 2-3 hours to visit.
4. Discover the Kirkstall Abbey - It is a ruined Cistercian monastery from the 12th century. You can see the ruins of the church, cloisters, and buildings. It will take around 1-2 hours to visit.
5. Shop at the Trinity Leeds - It is a shopping center with various shops, restaurants, and bars. You can shop and dine at the center. It will take around 2 hours to visit.
These are just some suggestions, and you can choose what interests you the most. You can mix and match as you like and allocate your time based on your preference.