Grand operas by Wagner inspiring adult group (9)
I believe the answer is:
gathering
'group' is the definition.
The answer is an example.
'grand operas by wagner inspiring adult' is the wordplay.
'grand' becomes 'g' (synonyms).
'operas by wagner' becomes 'thering' (The Ring cycle of operas by Richard Wagner).
'inspiring' means one lot of letters goes inside another.
'adult' becomes 'a' (abbreviation).
'g'+'thering'='gthering'
'gthering' placed around 'a' is 'GATHERING'.
(Other definitions for gathering that I've seen before include "bee" , "Assembly, meeting" , "Understanding - crowd" , "Assembly or concentration" , "Harvesting" .)