hired gun
noun [ C ]
US informal ukusan expert who is brought into a company or an organization to deal with a particular problem or situation:
Board members installed in the midst of takeover fights are hired guns with a clear agenda.
a person who is paid to do a particular job, especially something that others may consider to be morally wrong:
They accused the other party of using hired guns to turn in fraudulent registrations that they plan to make sure are thrown out before the balloting starts.