Possible Clues:

• Steed's footwear features Avenger's extremity in two forms of hose
• Plate nailed to equine hoof
• Supposedly lucky piece of metal
• It can spread and cause a delay
• Hack is shown over Oxford, possibly? Lucky thing
• Good luck bringer?
• Plate rumoured to be very 'you', luckily
• Lucky thing, so he - or she - makes out
• Blacksmith's creation
• There's something afoot in the stable