Student scoffed right after that (5)
I believe the answer is:
later
'after that' is the definition.
(thesaurus)
'student scoffed right' is the wordplay.
'student' becomes 'l' (as in L-plates for learner drivers).
'scoffed' becomes 'ate' ('to scoff' is to eat).
'right' becomes 'r' (common abbreviation).
'l'+'ate'+'r'='LATER'
(Other definitions for later that I've seen before include "At a subsequent time" , "At a time in the future" , "after an interval" , "Alter (anag.)" , "When to see you?" .)