Possible Clues:

• Wife of performer with opening feature that's amazing
• *Quality that really excites people
• Fat cow messing in back row reveals something special
• Pizazz ... or what 18-, 23-, 46- and 56-Across each has?
• Extremely impressive quality, informally ... or, when read differently, what the four longest puzzle answers all have
• Provider of '!!!'
• Acoustic effect by fine player that gives a thrill