'To enter the lists' definitions:

Definition of 'To enter the lists'

From: GCIDE

List \List\ (l[i^]st), n. [F. lice, LL. liciae, pl., from L. licium thread, girdle.] A line inclosing or forming the extremity of a piece of ground, or field of combat; hence, in the plural (lists), the ground or field inclosed for a race or combat. --Chaucer. [1913 Webster]
In measured lists to toss the weighty lance. --Pope. [1913 Webster]
To enter the lists, to accept a challenge, or engage in contest. [1913 Webster]