Some find amnesia a mild curse (4)
I believe the answer is:
damn
'curse' is the definition.
('damn' can be a synonym of 'curse')
'some find amnesia a mild' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'DAMN' can be found hidden inside 'find amnesia mild'.
(Other definitions for damn that I've seen before include "Consign to hell" , "Curse; strongly criticise" , "hang" , "Mild expletive" , "Censure" .)