Possible Clues:

• Homeric character cheers Ulysses at first
• Nineteenth letter of the Greek alphabet
• Greek letter
• -- cross, St. Anthony�s cross
• Letter after sigma 8. Last name of 12-Across
• Letter from aunt, no name
• Sigma upsilon separator
• ___ lepton
• Letter for 28-down
• Tee for Zorba?