Test last of aluminium cut in reverse (4)
I believe the answer is:
exam
'test' is the definition.
(I know that test can be written as exam)
'last of aluminium cut in reverse' is the wordplay.
'last of' says to take the final letters.
'cut' becomes 'axe' (both can mean to cancel or remove).
'in reverse' shows that the letters should be reversed in order.
The final letter of 'aluminium' is 'm'.
'm'+'axe'='maxe'
'maxe' back-to-front is 'EXAM'.
(Other definitions for exam that I've seen before include "paper" , "In brief, a test as in school" , "Test (abbrev.)" , "Formal knowledge test" , "School test (colloq.)" .)