Successful student jumps into river in disgrace (7)
I believe the answer is:
degrade
'disgrace' is the definition.
(I know that disgrace can be written as degrade)
'successful student jumps into river' is the wordplay.
'successful student jumps' becomes 'grad' (I am not sure about this - if you are sure you should believe this answer much more).
'into' is an insertion indicator.
'river' becomes 'Dee' (River Dee).
'grad' going inside 'dee' is 'DEGRADE'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for degrade that I've seen before include "Disgrace, lower in status" , "Reduce in worth" , "Deprive of dignity" , "Demean, cheapen" , "Humiliate" .)