Sort of Christian jazz fan about to embrace non-Christian festival (8)
I believe the answer is:
catholic
'sort of christian' is the definition.
(Catholicism is a Christian denomination)
'jazz fan about to embrace non-christian festival' is the wordplay.
'jazz fan' becomes 'cat' (I've seen this before).
'about' becomes 'c' (abbreviation for circa).
'to embrace' indicates putting letters inside.
'non-christian festival' becomes 'Holi' (Hindu festival).
'cat'+'c'='catc'
'catc' placed around 'holi' is 'CATHOLIC'.
(Other definitions for catholic that I've seen before include "Eclectic" , "of interest to all" , "Showing widespread sympathy" , "All embracing" , "Prayer" .)