Money the school raised (4)
I believe the answer is:
note
'money' is the definition.
(thesaurus)
'the school raised' is the wordplay.
'the school' becomes 'eton' (famous UK public school).
'raised' shows that the letters should be reversed in order.
'eton' back-to-front is 'NOTE'.
(Other definitions for note that I've seen before include "Comment" , "Short record or letter" , "Pay attention to, tone" , "Bill" , "A flat, for example" .)