a person who helps another (especially as a deputy or as a junior worker)

helper

a person working with another or others

associate, fellow worker

a person who goes, or is often or always with, another

helper, friend

a person who is (to be) given another person's authority etc

assistant, agent

a person who helps

assistant

a faithful supporter, especially one who obeys without question the orders of a leader

follower

an army officer below a captain; junior officer in the Navy

assistant

a person who takes part (in an activity)

person who takes part in activity

a person in an unimportant position, compared to others

subordinate