There are royalty-free music licensing sites with fancy ads and claims but most of them haven't done the due diligence to clear the music and vet the copyright claimant before they sell it to you.
If you want guaranteed protection and a reliable license then you would need to reach out to the composer directly via their PRO or sync agent. You can also use services like Keyframe Audio that is both a music licensing platform and rights management company and they guarantee licensed coverage and will indemnify you if you ever have an issue. Totally unique in the digital licensing world.