Possible Clues:

• Let it be around, dear, but you must put your foot down over it (7)
• Rocking lever operated by foot
• Bit of machine is something carried by poster maybe and left in box?
• Spinning-wheel pedal
• Pedal operating machine
• Foot lever working machine
• Something afoot if other than stable lad let in by bay or chestnut?
• Foot lever that works machine
• Put one's foot down and let it be about the start of 15 across
• One works just under one foot of this