Rust (7)
I believe the answer is:
corrode
'rust' is the definition.
(I know that rust can be written as corrode)
This is the entire clue.
(Other definitions for corrode that I've seen before include "Eg, to rust" , "Oxidise" , "Gradually weaken (by chemical action)" , "Cause to rust" , "Growth in hazel buds" .)