Wrong to repeat a G&S work? (8)
I believe the answer is:
operetta
'a gs work?' is the definition.
(Gilbert and Sullivan wrote operettas)
'wrong to repeat' is the wordplay.
'wrong' indicates anagramming the letters.
'to'+'repeat'='torepeat'
'torepeat' is an anagram of 'OPERETTA'.
(Other definitions for operetta that I've seen before include "Light entertainment" , "Theatre piece" , "Eg, Orpheus in the Underworld" , "Sung entertainment" , "La belle Helene, say" .)