clientContext = new SP.ClientContext.get_current();

(function () {

ExecuteOrDelayUntilScriptLoaded(CSR_Setup, "SP.js");
function CSR_Setup(){
    var overrideNameField = {};
    overrideNameField.Templates = {};
    overrideNameField.Templates.Fields = {
        "InstructionLibID": { "View": overrideNameFieldTemplate }
    };
    SPClientTemplates.TemplateManager.RegisterTemplateOverrides(overrideNameField);
}

function overrideNameFieldTemplate(ctx) {
    var InstructionLibID = ctx.CurrentItem.InstructionLibID;
    var fileRef = getFileLeafRefbyID("Instruction",InstructionLibID);
    if (InstructionLibID) {
        return "<a href='"+ fileRef + "'>Download</a>";
    }
    else {
        return "N/A";
    }
}

function getFileLeafRefbyID(LibName,Id){
        clientContext = new SP.ClientContext.get_current();
      oWebsite = clientContext.get_web();
      oList = oWebsite.get_lists().getByTitle(LibName);

        this.oListItem = oList.getItemById(Id);
        clientContext.load(this.oListItem);
        clientContext.executeQueryAsync(
        Function.createDelegate(this, successHandler),
        Function.createDelegate(this, errorHandler)
    );

        function successHandler() {
            return(oListItem.get_item('FileLeafRef'));
        }

        function errorHandler() {
            console.log('Fail');
        }
}
})();