Possible Clues:

• You've got to put your foot down over this
• Old sewing machine mechanism
• You've got to put your foot down to make this one work
• One's made to put one's foot down over this
• That'll get to work underfoot
• A dull coat in olive, for example, for a sewer's help
• Downtrodden machine operator
• That's what made you put your foot down
• Down-trodden machine-worker
• Part of machine that could be altered