Access Recruitment CRM runs on a relational database and will not allow the deletion of records that may be referenced elsewhere in the database.
Before you can delete the record you would need to remove all references within the database. It may therefore be preferable to hide the record from view in order to help with GDPR compliance following a request from the applicant, in the following way:
Open the applicant record
Click on the Deletion Request icon
If the requirements of your deletion request options allow it, the record will be processed and thereafter hidden from view with no access.