The most common and most likely answer to this crossword clue is the 15 letter word GOTTERDAMMERUNG
G
O
T
T
E
R
D
A
M
M
E
R
U
N
G
Buddy explains!
The straight part
We know that "work in Wagner’s Ring Cycle" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case work in wagner’s ring cycle = gotterdammerung.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.