The young midfielder spent time on loan at Carlisle United last season and is high up on manager Greg Abbott's list of potential summer signings.
"It's nice to be back and I'm looking forward to next season already," Clayton told the News & Star.
"I've been at City since I was seven so this will always feel like my club.
"I can't wait to start training and show the manager what I can do because obviously he hasn't really seen anything of me so far.
"Hopefully there will be opportunities during our pre-season matches to play and I'll be doing everything I can to impress the boss."