The name Clinton in Longford has one of two origins, Anglo or Scottish. If its Anglo, it will be hard to trace enough, but if its the Scottish clan, very easy indeed.
Their history is glorius and horrific, whether looking from a British or Irish standpoint, they came - the Scottish clan - with Cromwell, and were granted lands in Longford for "service" at Drogheda. During the Penal Times, they too were percecuted being Presbyterian, and switched sides, fighting for the rebels during 1798.
Some of the family emigrated on the George and Ann, a ship that brought the greater majority of the Scots Presbyterians in Longford to America. A descendant of theirs rose to be vice president of America circa 1830 - google him.
Their cousins the Dennistons - still a popular name in Longford, and prominent, and of the same origin - were very rpminent in the Turn Oot and suffered greatly for their part. The Clintons by now established in America helped some of them emigrate. The rest predominantly today are Catholic, though some are Anglican and a few still Presbyterian.
Clonton is an RC name today, as far as I know in Longford.