Related Clues:

• Brief letters
• Flagship product from 21-Down
• Bills or coins
• Sound of music
• One on a musical scale
• Ones, twos and fives, e.g.
• Explanatory material
• ATM filler
• Brief missive
• Word with cow or crop
• Scoring units
• Musical production
• It may be petty
• What the starts of 17-, 34- and 61-Across are
• Change, e.g.