Top grade ultimately raised in test (4)
I believe the answer is:
exam
'test' is the definition.
(I know that test can be written as exam)
'top grade ultimately raised' is the wordplay.
'top' becomes 'max' (short for maximum).
'ultimately' suggests the final letters.
'raised' says the letters should be written backwards (going up in a down clue).
The last letter of 'grade' is 'e'.
'max'+'e'='maxe'
'maxe' backwards is 'EXAM'.
'in' acts as a link.
(Other definitions for exam that I've seen before include "Scholastic test" , "Test (abbr)" , "Student test" , "Test (abbrev.)" , "'Test, in short (4)'" .)