If Clarke can't break into the current Irish squad then maybe he should consider early retirement from international football. As all ready posted, they are severely lacking in class.
Lots of players have been dropping out of squads willy-nilly, James McCarthy is missing from every second squad but is selected in this one ( I know he had good reason for wanting to miss the Euros, but he has previously pulled out of several squads). Marc Wilson is another that springs to mind.
Maybe Trap just doesn't fancy him as a player.