Finally found a video of this tune by Neill Connor. It's in the key of G (or at least in G tuning based on the scale he plays at the beginning). I have listened only once far to the video, but it sounds like it may be in 6/8 time which requires a number of adjustments for clawhammer. I may have a chance to to try some tab, but here's the YouTube link if someone else wnats to give it a go.
Thanks, Jack. I found some sheet music/tabs for mandolin and tenor banjo, and they show 4/4 time with measures made up of 4 eighth notes (??). I hope to dive more deeply into it. The instrumental in the link above doesn't seem to bear a lot of resemblance to my ear yet to the vocal version of the tune by the Pogues, but I have only scratched the surface. I will keep your suggestion in mind.