Born in Mullingar, County Westmeath, Clarkin was the son of Andrew Clarkin and Rose Anne Corrigan He stood for election to Dáil Éireann as a Fianna Fáil candidate for the Dublin South constituency at the 1944 general election but was unsuccessful. He was elected to Seanad Éireann by the Administrative Panel at 1944 Seanad election. He was re-elected to the Seanad at the 1948, 1951 and 1954 Seanad elections by the Industrial and Commercial Panel. He was an unsuccessful candidate at the 1952 Dublin North–West by-election. He died in 1955 during the 8th Seanad.
He served as Lord Mayor of Dublin from 1951 to 1953.
| Lord Mayor of Dublin