Test for former spouse in the morning (4)
I believe the answer is:
exam
'test' is the definition.
(I know that test can be written as exam)
'former spouse in the morning' is the wordplay.
'former spouse' becomes 'ex' (an ex-spouse).
'in the morning' becomes 'am' (AM on a clock).
'ex'+'am'='EXAM'
'for' is the link.
(Other definitions for exam that I've seen before include "One test" , "Students sit it" , "Set of questions evaluating skill or knowledge, in short" , "One might be taken for English" , "School test (colloq.)" .)