I worked out all the solutions, but for two of them I couldn't understand why. One was 8a, which many other people posting found puzzling too, so that isn't surprising. However, nobody has mentioned the other one that I'm stuck on as being difficult, so I must be stupidly missing something really easy. It's 19d. I see a perfectly easy definition at the end of the clue, but I can't understand the rest. Any gentle hints, anyone?