Related Clues:

• Measuring standard
• See 39-Across
• Second, e.g.
• College course division
• Building block
• Subdivision
• Motel room
• The 'U' of CPU
• Troop group
• Hand or foot
• Course, in education lingo
• Part of I.C.U.
• Platoon or squadron, e.g.
• Complex division
• Squad