PDF/A-1 requires PDF version 1.3 or 1.4. Also, it does not support things like transparencies. I guess, this might be the reason, why not even the latest Creative Cloud apps (I just checked InDesign, PhotoShop, and Illustrator) or FrameMaker support this any longer out-of-the-box. The only support that is there in the Creative Cloud apps currently is PDF/X-1a/b, PDF/X-2, PDF/X-3, and PDF/X-4.
However, you can use Acrobat Pro DC to convert a PDF to a PDF/A:
https://helpx.adobe.com/in/acrobat/using/pdf-x-pdf-a-pdf.html
Note, that for PDFA/1-a you need activate the Tagged PDF option in FrameMaker's Publish Settings, as PDF/A requires tagged PDFs.