Shelley's alma mater (4)
I believe the answer is:
eton
'shelley's alma mater' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for eton that I've seen before include "English college of note" , "College, collar or crop" , "British public school of note" , "Famous English public school" , "Posh English school of note" .)