<div ng-controller="ctrl">
    <mydirc></mydirc>
    <button ng-click="clickMe()">call clickMe()</button>
</div>

app.directive('mydirc',function() {
    return {
        restrict: 'E',replace: true,template: '<div></div>',link: function($scope,element,attrs) {
            $scope.clickMe= function() {
                alert('inside click');
            }
        }
    }
});