SQL SERVER 2016 high CPU
Please verify the settings for MAXDOP. Please review suggestions by Microsoft. In most cases the optimal value is the number of dedicated cores, that are available to SQL Server. But maximum value is set to '8'. In some cases that could vary and needs to be tested well to set to higher values.

I assume, that you have two six-core Processors with Hyper-Threating enabled. It is possible, that your queries don't perform very well, with Hyper-Threating enabled.
In some cases the SQL Server Performance is better using 12 'real' cores, than 24 combined with Hyper-Threating.

You should try to disable Hyper-Threating and verify the new settings.

Unfortunately you wrote, that this is your production environment. Are you able to verify settings on similar hardware and similar settings?

Furthermore you should have a look on your I/O subsystem. Are there more than one tempdb?

Additional (I can not comment another comment):

DBCC FREEPROCCACHE will effect all user.
Try using with option recompile at the SQL Query that effects the Performance issue most.