Mark O’Brien in his 2001 book De Valera, Fianna Fáil and the Irish Press makes fleeting reference to an Irish Press reporter named Paddy Clare who ‘took sabbatical leave’  in order to join the International Brigade during the Spanish Civil War.
Immediately, I became fond of this chap who decided to take a ‘leave of absence’ from work, not to go on holiday but to join the International Brigade and his risk his life in the defence of the Second Spanish Republic.
A bit of digging unearthed that Clare was firstly, a life long Irish Republican who fought in both the War of Independence and in the Civil War on the Anti-Treaty side and secondly, an individual who has largely been forgotten.
Born in Dublin into a republican family in 1908, his father Mick was an old Fenian. Joining Na Fianna Éireann in his early teens, he saw action in Dublin during the War of Independence. Following the treaty, he took the Republican side in the Civil War and was a member of the Four Courts garrison in 1922. Subsequently, he was imprisoned in both Kilmainham and Mountjoy where, in the latter, he once went on hunger strike. 
Always a keen writer, Clare contributed articles to An Phoblact and The Nation. His work caught the eye of De Valera who asked him to join the fledgling Irish Press in 1931. He would stay with the paper for the next forty-three years, first as diary clerk, then a reporter and finally as ‘night-town man’.
Still committed to Irish Republican Socialist politics, he made the decision to take a period of leave from the newspaper to join the International Brigade.
Unfortunately that is all I know about his involvement in the SCW. I’ve emailed Ciaran Crossey (from the Irish SCW website) to see if he has any more information
Returning to Dublin and to The Irish Press, he was appointed as the paper’s ‘night-town’ reporter, a post in which he’d keep until 1973. A tough job, Clare would man the office throughout the night and chase any leads or stories that occurred during the hours of darkness.
Clare passed away in 1983 at the age of seventy-five. Tim-Pat Coogan wrote at the time:
Gravely voiced, indefatigably cheerful, with the yellow pallor of the night worker, which he was for scores of years, Paddy Clare to generations of young Irish Press journalists, epitomised the ideal of the hard-shelled, heart-of-gold professional reporter.
An IRA veteran of at least two wars (possibly three) and a respected journalist of over forty years, Clare lived a full life.