Sharepoint - Uncaught TypeError: Cannot read property 'get_current' of undefined

Since you are using SP.ClientContext in CSR, make sure the SharePoint script file 'sp.js' is loaded before your rendering code runs:

SP.SOD.executeFunc('sp.js', 'SP.ClientContext', function(){
 //Your code goes here...
});

fixed with this

$(document).ready(function () { ExecuteOrDelayUntilScriptLoaded(CustomAction, "sp.js"); });

    function CustomAction()

    {
           //Your Code
    }

This works for me when I am using WorkflowServices. It should work in your case as well:

ExecuteOrDelayUntilScriptLoaded(function () {
    ExecuteOrDelayUntilScriptLoaded(function () {
        SP.SOD.registerSod('SP.ClientContext', SP.Utilities.Utility.getLayoutsPageUrl('sp.js'));
        SP.SOD.registerSod('SP.WorkflowServices.WorkflowServicesManager', SP.Utilities.Utility.getLayoutsPageUrl('SP.WorkflowServices.js'));
        SP.SOD.loadMultiple(['SP.ClientContext', 'SP.WorkflowServices.WorkflowServicesManager'], function () {
            var context = SP.ClientContext.get_current();
            var web = context.get_web();
            var servicesManager = SP.WorkflowServices.WorkflowServicesManager.newObject(context, web);
            var instanceService = servicesManager.getWorkflowInstanceService();
        });
    }, "sp.js");
}, "sp.runtime.js");