Tests cut up manuscript (5)
I believe the answer is:
exams
'tests' is the definition.
('exam' can be a synonym of 'test')
'cut up manuscript' is the wordplay.
'cut' becomes 'axe' (I've seen this before**).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'manuscript' becomes 'ms' (abbreviation for manuscript).
'axe' backwards is 'exa'.
'exa'+'ms'='EXAMS'
(Other definitions for exams that I've seen before include "papers" , "Set of exercises evaluating knowledge (abbr)" , "GCSE, A-level, etc" , "Tests for students" , "Cut up writing" .)