A tutor can provide constructive suggestions and instruction about the writing process, both in general and in response to early drafts of the paragraph. This can extend to written corrections on early drafts but should not include actual composition. The actual paragraph should come from the student.
The purpose of a tutor is to help students complete their own work by providing the best teaching and coaching possible. The best tutors help students find their own optimal methods for organizing their thoughts and generating compositions. When it comes to the actual creation of work for graded assignments, though, the student must do the work independently.