Possible Clues:

• Freight charge deduction
• 'Tis, and 'tis a matter of weight
• Gross minus net
• Perhaps 'tis more than once a weighty matter
• Butcher-scale word
• Variety of vetch
• Produce scale deduction
• `Tis ans 'tis? Wait for it, by the sound of it
• Trucker's concern
• Sounds as if the rip is all a matter of weight