Spreader of malicious gossip (13)
I believe the answer is:
scandalmonger
'spreader of malicious gossip' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for scandalmonger that I've seen before include "Rumour spreader" , "One who spreads malicious gossip" , "Muckraker" , "Destroyer of reputation" , "Person spreading malicious tittle-tattle" .)