Former spouse takes morning quiz (4)
I believe the answer is:
exam
'quiz' is the definition.
(I've seen this in another clue)
'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 "Something to sit" , "Oral maybe" , "Important test" , "Student test" , "School test (colloq.)" .)