Silly to repeat a work by Gilbert and Sullivan, maybe (8)
I believe the answer is:
operetta
'a work by gilbert and sullivan maybe' is the definition.
'silly to repeat' is the wordplay.
'silly' indicates anagramming the letters.
'to'+'repeat'='torepeat'
'torepeat' is an anagram of 'OPERETTA'.
(Other definitions for operetta that I've seen before include "Eg, Orpheus in the Underworld" , "Light classical music comedy-drama" , "G&S work, perhaps" , "Sung entertainment" , "Eg, The Gondoliers" .)