Depending on the configuration of the account, when an objective is still in draft it can be deleted by the employee and their manager. However, for most configurations, draft objectives and confirmed objectives can only be deleted by managers and moderators.
To delete an objective for your team member, go into their objectives page.
Click into the objective to open it up and click the 'Options' menu on the top right.
Click 'delete'.
Confirm you want to proceed with the deletion by clicking ok and then the objective will be deleted.
Note: Once deleted, an objective cannot be recovered.