He may well be 3rd choice at the moment if you think bringing in Gunn was the correct decision but he should have at least 1 or 2 caps to his name by now if Clarke was in any way competent.
Excellent club form is never a guarantee of excellent international form, but nobody could deny that he should have been tried out in some of the games he's been called up for, the Same applies to a fair few of the outfield players as well.