I'm no night owl, Kingfisher, but I believe a nightclub has live entertainment if any, while a disco features dancing to recorded music. 'Clap' and 'applaud' are often the same, with 'applaud' more formal; 'applaud' can be used in a wider sense-- the committee applauded the chairman's decision', where they did not actually 'clap'. The latter is restricted to the physical beating of hands together.
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