Former spouse takes morning test (4)
I believe the answer is:
exam
'test' is the definition.
(I know that test can be written as exam)
'former spouse takes morning' is the wordplay.
'former spouse' becomes 'ex' (an ex-spouse).
'takes' is a charade indicator (letters next to each other).
'morning' becomes 'am' (as in 12:00 AM).
'ex'+'am'='EXAM'
(Other definitions for exam that I've seen before include "'Test, in short (4)'" , "School test (colloq.)" , "End-of-course assessment" , "Oral maybe" , "(Academic) test" .)