Yes, you can schedule a Clarity job to run is such a way it runs after another job using the Jobs Definition page in the Admin Tool in combination with the Scheduled Jobs page in the application.
For the Scenario described, you would make Job A incompatible with both Job B and Job C in the Admin Tool. You would then schedule jobs B and C to run at their appointed start times in the application. Without knowing specific details, assume Job B and Job C each take 5 minutes to complete their runs. With this information, you could then schedule Job A to run, for example, 2 minutes after the scheduled start times of jobs B and C. Since Job A is incompatible with jobs B and C, Job A will be in Waiting status when it kicks off at its scheduled time and won't begin until after Job B and Job C complete their runs.
Hope this helps.
Don