Possible Clues:

• When pigs fly, poetically
• When Romeo says he 'saw true beauty' before seeing Juliet
• "In thy dreams!"
• At no time, in old times
• Can no work be found for one in the artillery (2' 2)
• '... ___ the twain shall meet'
• -- -do-well (idle sort)
• ___-do-well (loafer)
• Opposite of 'alway'
• 'What, will these hands ___ be clean?': Lady Macbeth