Hired Gun Meaning

(idiomatic, by extension) A person who is employed to advance the interests of his or her employer, especially in a vigorous manner using such methods as political lobbying, legal advocacy, or persuasion.

Example: A person who is employed as an armed guard, enforcer, or mercenary and who is prepared to use gunplay or similar violent methods in order to assert the interests of his or her employer.
2008 Dec. 9, Rania Abouzeid, "Iraqis Welcome Blackwater Indictments," Time:
  The hired guns, who protect diplomats, dignitaries and businesspeople, tear through the streets of the capital in convoys of armored SUVs.
1999 Nov. 22, Viveca Novak, "The Claritin Case," Time:
  [O]ne of Gore's senior advisers, top-tier lobbyist Peter Knight, is a hired gun for pharmaceuticals giant Schering-Plough.