A user account can work on more than one profile. Examples are a band, where each member's account is linked to the band's profile, or a manager working on artists' profiles. A linked user can add and change items on the profile as if it were their own.
Open ACP > Modules > Profiles > Profiles > Tools > Link User Accounts.
Repeat for each profile the user should have.
Open the user's Account page as master admin. When the account is linked to more than one profile, a Linked Profiles list shows them. Uncheck a profile and save to take the user's access away.