SA-9 External system services
What the standard requires
a. Require that providers of external system services comply with organizational security and privacy requirements and employ the following controls: [controls]; b. Define and document organizational oversight and user roles and responsibilities with regard to external system services; and c. Employ the following processes, methods, and techniques to monitor control compliance by external service providers on an ongoing basis: [processes, methods, and techniques].
Quoted verbatim from NIST SP 800-53 Rev 5 (OSCAL catalog), which is in the public domain.
Cross-framework mappings
No cross-framework mapping is seeded for this control. That is stated rather than filled in: a mapping nobody authored is worse than a gap you can see.
In CMDash this control is a row with an owner, a status, uploaded evidence kept with its full history, and an export an assessor can read.