If you describe someone as a camp follower, you mean that they do not officially belong to a particular group or movement but support it for their own advantage.
[disapproval]
...the Tory leader's friends and camp followers.
2. countable noun
Camp followers are people who travel with an army or other group, especially members of soldiers' families, or people who supply goods and services to the army.
camp follower in British English
noun
1.
any civilian, esp a prostitute, who unofficially provides services to military personnel
2.
a nonmember who is sympathetic to a particular group, theory, etc
camp follower in American English
1.
a civilian who goes along with an army, esp. as a vendor of goods or services or as a prostitute
2.
a nonmember who is associated with a certain group