Disloyalty (8)
I believe the answer is:
betrayal
'disloyalty' is the definition.
(I know that betrayal is a type of subversiveness)
This is all the clue.
(Other definitions for betrayal that I've seen before include "Treacherous act" , "Treacherous divulgence" , "Double-crossing" , "Breaking of trust" , "Act of treachery" .)