The words 'hired' and 'gun' act as a noun. It has slang use. The words hired gun mean point towards a person, especially a professional killer. Professional killer is person who is hired or paid to kill another person. He could also be an individual who is hired or paid to protect another person or to fight for someone.
Hired gun is an individual who is good at obtaining or gathering power for other people. The meaning of hired gun is just not restricted to the violent spheres of power and politics. Hired gun could also be the person who possesses special knowledge or expertise and who is hired or paid to solve difficult problems and complex situations. This person could be an expert in law or a mastermind in business or government.
Hired gun is an individual who is good at obtaining or gathering power for other people. The meaning of hired gun is just not restricted to the violent spheres of power and politics. Hired gun could also be the person who possesses special knowledge or expertise and who is hired or paid to solve difficult problems and complex situations. This person could be an expert in law or a mastermind in business or government.