School memorandum stuck up (4)
I believe the answer is:
eton
'school' is the definition.
(famous UK public school)
'memorandum stuck up' is the wordplay.
'memorandum' becomes 'note' (I've seen this before).
'stuck up' says the letters should be written in reverse.
'note' back-to-front is 'ETON'.
(Other definitions for eton that I've seen before include "Town opposite Windsor on the Thames" , "Independent school" , "Town on the Thames noted for its school" , "Berks college" , "School near Slough" .)