Regional accent entertains South American treasurer (6)
I believe the answer is:
bursar
'treasurer' is the definition.
(someone in charge of money)
'regional accent entertains south american' is the wordplay.
'regional accent' becomes 'burr' (informal term for a regional accent).
'entertains' means one lot of letters goes inside another.
'south american' becomes 'SA'.
'burr' going around 'sa' is 'BURSAR'.
(Other definitions for bursar that I've seen before include "Official managing school finances" , "administrator" , "Treasurer of educational establishment" , "College financier" , "College financial official" .)