Restitution finishes in the morning (6)
I believe the answer is:
amends
'restitution' is the definition.
(synonyms)
'finishes in the morning' is the wordplay.
I cannot really see how this works, but
'finishes' could be 'ends' ('end' can be a synonym of 'finish') and 'ends' is located in the answer.
'morning' could be 'am' (as in 12:00 AM) and 'am' is found within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for amends that I've seen before include "Sad men (anag.)" , "Make these to atone for wrong done" , "Makes minor improvements" , "Fixes" , "Compensation" .)