Related Clues:

• Put a strain on
• Reason to cram
• Bar code?
• Lab work
• Song and album by the Doors
• Bad thing to break
• See 19-Down
• Rule
• See 56-Across
• Midterm, for one
• Use a cupel
• Dreaded class word
• Step in getting a license
• Police, with 'the'
• Final, perhaps