Rotten scandal at university on the way back (6)
I believe the answer is:
putrid
'rotten' is the definition.
('putrid' can be a synonym of 'rotten')
'scandal at university on the way back' is the wordplay.
'scandal' becomes 'dirt' ('dirt' can be a synonym of 'scandal').
'at university' becomes 'up'.
'on the way back' says the letters should be written backwards.
'dirt'+'up'='dirtup'
'dirtup' back-to-front is 'PUTRID'.
(Other definitions for putrid that I've seen before include "Foul" , "Decomposed, rotting" , "Decaying, rotting" , "contaminated" , "Really rotten and foul-smelling" .)