You can close close the tab by connecting the tabCloseRequested ( int index ) signal to a slot like
connect(tabWidget, SIGNAL(tabCloseRequested ( int )), this, slot(closeTab(int))).
The whole point I think is to validate the closing of the tab.
eg the following slot will close the clicked tab except if it is the first tab
void closeTab(int index)
{
if (!index)
tabWidget->removeTab(index);
}