Ken is correct, use either of the following commands within the Python Command Prompt to upgrade the arcgis module to 1.6.1:
conda install arcgis --no-pin
conda upgrade arcgis --no-pin
Dan is also correct that you do not need to create a cloned environment IF you have administrative privileges on the computer. Many of our users do not have administrative privileges so we recommend creating the cloned environment that they will have access to manage. We also recommend creating the cloned environment so that the default does not become corrupted.
However if you do want to update the default arcgispro-py3 environment, run the Python Command Prompt as Administrator and run one of the above commands.