Right, so rabble-rouser at the end is your definition — someone who whips the crowd up. Now for the build: DEM is the abbreviation for Democrat, then AGOG gives you "very eager", and finally you need the occasional letters of "pure" — just take every other one, so U and E — tacked on the end. Stick DEM, AGOG and UE together and you've got your rabble-rouser.