Harm or spoil (6)
I believe the answer is:
damage
I believe this clue is a double definition.
'harm' is the first definition.
(I know that harm can be written as damage)
'spoil' is the second definition.
(I know that spoil has the is a more specific form of the action damage)
(Other definitions for damage that I've seen before include "Harm, injury" , "Impairment, injury" , "Cost (slang)" , "To vandalise" , "Physical harm" .)