Possible Clues:

• Significant, like the 0 of 3,2,1,0? No!
• As an introductory remark, the ultimate reassurance of importance?
• Not extremely insignificant after all!
• Finally devises stunts to beat all
• Emcee's ''Finally . . .''
• Words before the final item ... or like the second number in 17-, 23-, 34- or 44-Across
• *Words before a grand finale
• "And finally . . ."
• "And finally ..."
• Finally (and equally impressively) alto blasts tune improvised around tango