wag-at-the-wall, n. — Green’s Dictionary of Slang

wag-at-the-wall n.

also wag, wag-of-the-wall

(Irish) a clock.

1901		Falkirk Herald 19 June 7/6: This ould ‘wag-at-the-wall’ is always tin [sic] minutes fast.
1908		L. Doyle Ballygullion 107: The ould wag-at-the-wall was goin’ ‘tack-tack, tack-tack’, very slow and steady.
1932		M. Marshall Travels of Tramp-Royal 92: I got her settled down in the rocker below the wag-at-the wa’.
1966		P. Boyle At Night All Cats Are Grey 215: The loud ticking of a wag-o’-the wall.
1983		W.F. Marshall ‘Ceilidh’ in Livin’ in Drumlister 4: And the decent neighbour men / Make they kailey as like as not / Till the wag is striking ten.