In military terms, a Lieutenants Protection Association (sometimes also called a "Lieutenants Protection Agency" or "LPA") is an informal group of junior officers. Many young officers find the Lieutenant Protection Association/Agency community is the best way to make an impact and a successful start to their military career once in the fleet.
Depending the unit, the LPA may base membership on being a "one bar," and include Warrant Officers.
Unit LPAs may extend honorary membership, or limited membership, to servicemembers of other ranks. These individuals will be included based on vague, subjective qualifications.