Scrap upcoming motorway test (4)
I believe the answer is:
exam
'test' is the definition.
(I know that test can be written as exam)
'scrap upcoming motorway' is the wordplay.
'scrap' becomes 'axe' (both can mean to cancel or fire).
'upcoming' says the letters should be written in reverse.
'motorway' becomes 'M' (as in motorway names - Ma, M4 etc).
'axe' backwards is 'exa'.
'exa'+'m'='EXAM'
(Other definitions for exam that I've seen before include "Important test" , "paper" , "One taken by candidate" , "Educational test" , "Test (abbrev.)" .)