One of Trumps many sycophantic white house staff, who get such a raging boner from his position of power they basically act like he can do no wrong and will defend his position at the cost of everything; behaving like a simp only much worse, hence the term Sump.
Mitch McConnell: "Dude it's been almost 5 minutes and no-ones licked Trumps asshole! Where the hell is Seb Gorka?"
Mike Pence: "Nah, he's gone bro! Trump fired him, he was way too much of a Sump!"