Possible Clues:

• Not anybody can be top dog
• ''There's ___ here but us ...''
• Who has won an Oscar for Best Actor three times
• "Trust ___"
• Not a single person shows energy at midday
• Indefinite pronoun
• Before Oedipus, who could answer the riddle of the Sphinx
• "For __": Beatles song
• ''... tree falls in the forest and ___ ...''
• Who “needs to know,” according to Shania Twain