Preserve antidote (4)
I believe the answer is:
cure
I believe this is a double definition.
'preserve' is the first definition.
(curing is a kind of preserving)
'antidote' is the second definition.
(I've seen this in other clues)
(Other definitions for cure that I've seen before include "restore one to health" , "Restore to good health" , "Foreign priest" , "priest without an accent" , "priest from 22 [ALSACE]" .)