Virtuoso passage from A Study into Catholic South Africa (7)
I believe the answer is:
cadenza
'virtuoso passage' is the definition.
(musical passage)
'a study into catholic south africa' is the wordplay.
'study' becomes 'den' (term for a study or office).
'into' indicates putting letters inside.
'catholic' becomes 'C' (abbreviation as in RC for Roman Catholic).
'south africa' becomes 'za' (abbreviation for Zuid-Afrika).
'a'+'den'='aden'
'c'+'za'='cza'
'aden' going into 'cza' is 'CADENZA'.
'from' acts as a link.
(Other definitions for cadenza that I've seen before include "Virtuoso passage by solo performer" , "Soloist's virtuoso passage" , "Solo display passage" , "Virtuoso's solo" , "Impromptu insertion in piece of music" .)