Portion of dessert's ideal getting over sorrow (8)
I believe the answer is:
distress
'sorrow' is the definition.
(I have seen 'Extreme sorrow ' mean 'distress' so perhaps 'sorrow' could also mean 'distress')
'portion of dessert's ideal getting over' is the wordplay.
'portion of' says the answer is hidden in the clue.
'getting over' says the letters should be written backwards.
'ssertsid' is hidden in the letters of 'desserts ideal'.
'ssertsid' backwards is 'DISTRESS'.
(Other definitions for distress that I've seen before include "Affliction" , "Mental or emotional pain" , "Sadden" , "Cause mental pain" , "Mayday is such a signal." .)