Test no longer taking half a day (4)
I believe the answer is:
exam
'test' is the definition.
(synonyms)
'no longer taking half a day' is the wordplay.
'no longer' becomes 'ex' (prefix meaning former or onetime).
'taking' is a charade indicator (letters next to each other).
'half a day' becomes 'am' (I can't explain this - if you can you should believe this answer much more).
'ex'+'am'='EXAM'
Can you help me to learn more?
(Other definitions for exam that I've seen before include "Oral maybe" , "Written test" , "Something to sit" , "Important test" , "Student test" .)