Epic tale of silver found in South Africa (4)
I believe the answer is:
saga
'epic tale' is the definition.
(I've seen this before)
'silver found in south africa' is the wordplay.
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'found in' indicates putting letters inside.
'south africa' becomes 'SA' (abbreviation).
'ag' put into 'sa' is 'SAGA'.
'of' acts as a link.
(Other definitions for saga that I've seen before include "A long adventurous story - it's a gas" , "Norse epic" , "A long story or poem - it's a gas" , "Long narrative" , "Account of great heroism" .)