I synced the Lead object of CRM to Marketing Cloud. The marketing team will have access to marketing cloud. Now if the marketing team edits the value of Lead in Contact Builder within Marketing Cloud it should reflect the CRM. But when I try to do this in the Marketing Cloud, the Edit and Clear buttons on Synchronized data extension are disabled. How do I enable them?
The data from the Connector flows one-way and is not bi-directional. The only "bi-directional" data going back to SalesCloud is tracking information unless you use AMPScript for updating Salesforce Objects or Journey Builder to update the Lead.
Unfortunately, you cannot update a record in Synchronized Data Extensions to have it reflect the changes in CRM.