Possible Clues:

• Meeting of hands after the performance?
• Show of appreciation when a play half complete, during interval
• Paula's running around quietly before onset of extraordinary clapping etc
• Sign of audience approval
• Mark of appreciation like clapping and cheering
• It's produced by people giving a hand in the pit
• Praise a piano recital's ending during interval
• Acclaim a performer loves, at first, during interval
• Fresh appeal to bring America into line gets loud support
• There's little of the plural in a gap in the clapping