Gertrude ultimately learning about wrongdoing in Shakespearean setting (8)
I believe the answer is:
elsinore
'shakespearean setting' is the definition.
(Hamlet is set in Elsinore in Denmark)
'gertrude ultimately learning about wrongdoing' is the wordplay.
'ultimately' suggests the final letters.
'learning' becomes 'lore' (both can mean tradition or knowledge).
'about' indicates putting letters inside.
'wrongdoing' becomes 'sin' (sin is a kind of wrongdoing).
The final letter of 'gertrude' is 'e'.
'lore' placed around 'sin' is 'lsinore'.
'e'+'lsinore'='ELSINORE'
'in' acts as a link.
(Other definitions for elsinore that I've seen before include "Danish port, setting of Shakespeare's Hamlet" , "Relies on to find Hamlet's castle in Denmark" , "Hamlet's home" , "Location for Hamlet" , "setting for play" .)