Loathe exam following low grades (6)
I believe the answer is:
detest
'loathe' is the definition.
(I've seen this in another clue)
'exam following low grades' is the wordplay.
'exam' becomes 'test' (synonyms).
'following' says to put letters next to each other.
'low grades' becomes 'de' (D and E are low academic grades).
'test' after 'de' is 'DETEST'.
(Other definitions for detest that I've seen before include "Cordially laothe" , "Loathe, hate intensely" , "Hate a lot" , "Dislike heartily" , "Dislike intensely, loathe" .)