sp_configure 'clr enabled',1
and got message as below
Configuration option 'clr enabled' changed from 0 to 1. Run the RECONFIGURE statement to install.
While running RECONFIGURE I got below error
The reason was the run_value of configuration cant be changed without server stop and restart. The only option in that case is to use WITH OVERRIDE option. This wont force the config value checking.
More details can be seen in below MSDN link