Former spouse takes morning evaluation (4)
I believe the answer is:
exam
'evaluation' is the definition.
(I know that evaluation can be written as exam)
'former spouse takes morning' is the wordplay.
'former spouse' becomes 'ex' (an ex-spouse).
'takes' says to put 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 "Students sit it" , "One might be taken for English" , "'Test, in short (4)'" , "One test" , "paper" .)