Prod men to interrupt offensive opera (9)
I believe the answer is:
ruddigore
'opera' is the definition.
(I've seen this before)
'prod men to interrupt offensive' is the wordplay.
'prod' becomes 'dig' (synonyms).
'men' becomes 'or' (military abbreviation for Other Ranks).
'to interrupt' means one lot of letters goes inside another.
'offensive' becomes 'rude'.
'dig'+'or'='digor'
'digor' placed into 'rude' is 'RUDDIGORE'.
(Other definitions for ruddigore that I've seen before include "G&S operetta" , "G & S' alternative for "The Witch''s Curse"" , "show" , "One of 63 [OPERETTAS]" , "Gilbert and Sullivan opera" .)