Tinny performance captivating English number (6)
I believe the answer is:
ninety
'number' is the definition.
(ninety is a kind of whole number)
'tinny performance captivating english' is the wordplay.
'performance' indicates an anagram.
'captivating' is an insertion indicator (inserted letters are captured or captivated).
'english' becomes 'E' (abbreviation as in OED).
'tinny' anagrammed gives 'ninty'.
'ninty' going around 'e' is 'NINETY'.
(Other definitions for ninety that I've seen before include "Fourscore and ten" , "Excellent percentage score" , "Minutes played in a football match" , "Three thirties" , "quite an age" .)