About 100 turned tail in performance (7)
I believe the answer is:
recital
'performance' is the definition.
(I know that recital is a type of performance)
'about 100 turned tail' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'r00' becomes 'C' (Roman numeral).
'turned' indicates anagramming the letters.
'tail' with letters rearranged gives 'ital'.
're'+'c'+'ital'='RECITAL'
'in' acts as a link.
(Other definitions for recital that I've seen before include "Verbal account" , "Musical entertainment or a long account" , "Article (anag)" , "Performance, usually musical" , "Soloist's performance" .)