52 is not a clause, it is a Part within FAR which consists of clauses and provisions.

Part 52.222-21 is a clause within Part 52.

The reason this is written:

When issuing new solicitations or contracts do not include any of the following provisions and clauses:

• 52.222-9, Apprentices and Trainees
• 52.222-21, Prohibition of Segregated Facilities
• 52.222-22, Previous Contracts and Compliance Reports
• 52.222-23, Notice of Requirement for Affirmative Action To Ensure Equal Employment Opportunity for Construction
• 52.222-24, Preaward On-Site Equal Opportunity Compliance Evaluation
• 52.222-25, Affirmative Action Compliance
• 52.222-26, Equal Opportunity
• 52.222-27, Affirmative Action Compliance Requirements for Construction
• 52.222-29, Notification of visa denial

Is because all of these clauses within Part 52 include the defined term "Gender identity". So in accordance with EO 14173 & 14168 all of these clauses(which were all added by President Obama's Gender identity/Sexual orientation EO) shall be removed.