The defender has concurred on a three-month contract with The Gulls which he will sign upon his return for pre-season training.
Hankin has been handed the incentive of a prolonged stay at Plainmoor by boss Leroy Rosenior if he demonstrates he has recovered from injury.
The 22-year-old underwent a shin operation in the second half of last season and missed the closing weeks of the campaign.
The former Crystal Palace ace will be hoping to play a full part in pre-season to hand himself the best possible chance of a more permanent contract.
