The 29-year-old is the club's third new signing of the summer following the arrivals of Woking goalkeeper James Bittner and Hayes midfielder Liam Feeney.
Clarke started his career with Mansfield before making the move to Victoria Park but a new manager meant his opportunities became limited leading to loan spells at Stockport, Port Vale and Rochdale.
City boss Nick Holmes revealed Tommy Widdrington's influence was again a big factor in bringing Clarke to the Raymond McEnhill Stadium.
"Tommy knows him well and he's also played in the same team as Jon Bass," Holmes told the Salisbury Journal.
Meanwhile Matt Tubbs, Robbie Matthews, Mike Fowler and Ryan Clarke have all signed full-time contracts with the club.