A revocation transaction is a token allowance transaction that sets the approved amount to zero, thus revoking the original approval.
Click Risks in the left navigation menu to open the Risks page.
Filter the list to locate specific approvals.
Select the approvals you want to revoke.
Click Revoke or Revoke all for all the approvals. Make sure that the signing wallet holds enough tokens (gas) to cover the transaction fee.
This starts the revocation transaction process. The transaction (or each transaction in a batch) is checked by the transaction policy.