I looked up the meaning and readings for 徒 . In all cases I found the on reading as ト.
In Midori dictionary it is translated as “follower”.
In Jisho.org it translated as: “on foot, junior, emptiness, vanity, futility, uselessness, ephemeral thing, gang, set, party, people”.
In Tangorin.com, it is “junior; emptiness; vanity; futility; uselessness; ephemeral thing; gang; set; party; people”.
Is that an error in Midori?
Thanks for considering this.