Heartbreaking mace decay (7)
I believe the answer is:
corrode
'decay' is the definition.
(I know this)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for corrode that I've seen before include "Chemically weaken" , "Gradually weaken (by chemical action)" , "Oxidize" , "Eat away, rust" , "Oxidise" .)