Possible Clues:

• ''What a week!''
• Office workers' letters
• "Yay, tomorrow's Saturday!"
• End-of-wk. exclamation
• '___, I guess. At least the week's over.'
• Nine-to-fivers' favorite letters
• Letters anticipating the weekend
• Letters uttered with relief
• 'Whew! The workweek's almost over!'
• Office cry