Sometimes a student has submitted to the wrong assignment in a Canvas course, or submitted the wrong file, and staff sometimes need to find out how to proceed.

Within Canvas, currently there is not a way to outright remove trace of a submission. It is not even possible for the 'Tier 1' Instructure support team to do this, even via the API. What can be done:

A submitted file can be deleted - please email IT Services (servicedesk@liverpool.ac.uk). This replaces the submitted file with a new blank pdf. This could be very useful if the wrong file has been submitted and it contains sensitive information.
Grades, feedback and rubrics - feedback via these mechanisms can all be deleted one by one. If you are not the marker who left the feedback comments then it may require someone with admin access. Either raise an email with IT Services or contact someone in your department who has the 'Dept Admin' role in Canvas.

Even after doing the above, the student will still see a record of the submission, and this may prevented them from resubmitting to the assignment if you have limited the number of attempts.