Clontarf are Division One's new leaders as they brought Young Munster down to earth after last week's shock win over champions Cork Constitution.
'Tarf's heavier pack dictated play in the driving rain and high winds.
They seized their chance just before half-time, pouncing for the game's only try through hooker Aaron Dundon.
He scored under the posts after a maul and a series of recycles. Centre Daragh O'Shea tagged on the conversion.
Both sides had their spells of dominance but the Dubliners deservedly held on.
Scorers:
Clontarf: Try: Aaron Dundon; Con: Darragh O'Shea
