A clear is one that never started to develop. When you candle, those eggs won't show any veins or other signs of development. Quitters are eggs that have started to develop but died somewhere during development. Often you will see a ring around the inside of the egg. If I'm not positive, I'll wait a few days and candle again, comparing it to an egg I am sure is still developing.
With a broody, any eggs that are going to hatch should all do so within about 24 hours from the first one (if they were all set at the same time). If the hen leaves the nest with an egg still in it, I trust her judgement that it won't hatch. Anything after 23 days, I know won't hatch. Broody incubate hens just generally don't go that late. Unless, of course, she's off the nest for a long time for some reason and the eggs get cold. That can sometimes delay a hatch.