Green’s Dictionary of Slang

(Irish) a departure (on foot), an evasion; usu. as do a legger.

1991		R. Doyle Van (1998) 500: Yeh’d want to get out o’ the way there, he told her – You’ll be fuckin’ trampled on. The woman did a legger.
2001		G. Coughlan Everyday Eng. and Sl. 🌐 Legger, do a (phr): to abscond from the scene.
2011		T. Warner Beloved 157: I did a legger (ran away) real quick.
2017		L. McInerney Blood Miracles : ‘I dig up the sponds to do a legger’.