If config option "clearOnEscape" is true, then add a key listener that will clear this field
function() {
            if (!this.clearOnEscape) {
                return;
            }

            // Using a KeyMap did not work: ESC is swallowed by combo box and date field before it reaches our own KeyMap
            this.textField.inputEl.on('keydown',
                function(e) {
                    if (e.getKey() == Ext.EventObject.ESC) {
                        if (this.textField.isExpanded) {
                            // Let combo box or date field first remove the popup
                            return;
                        }
                        // No idea why the defer is necessary, but otherwise the call to setValue('') is ignored

						// 2011-11-30 Ing. Leonardo D'Onofrio leonardo_donofrio at hotmail.com
						if (this.textField.clearValue) {
							Ext.Function.defer(this.textField.clearValue, 1, this.textField);
						} else {
							Ext.Function.defer(this.textField.setValue, 1, this.textField, ['']);
						}
                        // end Ing. Leonardo D'Onofrio
						e.stopEvent();
                    }
                },
                this);
        }