Hi DiptiRanjan Swain,
As of the current state of features, it is not possible to enable Microsoft Defender for Container on a single cluster; it applies to the entire Azure subscription.
This is also stated in the documentation under https://learn.microsoft.com/en-us/azure/defender-for-cloud/defender-for-containers-introduction - and FAQ here: https://learn.microsoft.com/en-us/azure/defender-for-cloud/faq-general
Defender for Servers has recently entered preview, but the activation is currently only available through the REST API, not the Portal (yet).
Here is the documentaion: https://learn.microsoft.com/en-us/azure/defender-for-cloud/tutorial-enable-servers-plan#enable-defender-for-servers-at-the-resource-level
And a script to help: https://github.com/Azure/Microsoft-Defender-for-Cloud/tree/main/Powershell%20scripts/Defender%20for%20Servers%20on%20resource%20level
The only option, if you do not want to enable it for your entire subscription, is to separate them into different Azure subscriptions from what I know about.
Hope it helps a bit still. We can hope it comes here to in the feature.