Tortious Interference with Contractual Relations.

Trump and Daniels purportedly have a nondisclosure agreement in place. Trump could sue CBS for inducing Daniels to break the agreement by speaking.

To win on this claim, Trump would need to prove the following basic elements, which are a bit different from state to state:

The existence of a contractual relationship between two parties.
Knowledge of that relationship by a third party.
Intent of the third party to induce a party to the relationship to breach the relationship.
Lack of any privilege on the part of the third party to induce such a breach.
The contractual relationship is breached.
Damage to the party against whom the breach occurs.