Full of enthusiasm, getting a role initially in Wagnerian epic (6)
I believe the answer is:
raring
'full of enthusiasm' is the definition.
(raring to go)
'a role initially in wagnerian epic' is the wordplay.
'initially' indicates taking the first letters.
'in' means one lot of letters goes inside another.
'wagnerian epic' becomes 'Ring' (The Ring cycle by Richard Wagner).
The initial letter of 'role' is 'r'.
'a'+'r'='ar'
'ar' going into 'ring' is 'RARING'.
'getting' acts as a link.
(Other definitions for raring that I've seen before include "Eager (to go?)" , "Eager, impatient" , "Very eager (to do something)" , "Agog" , "Very keen (to go?)" .)