Possible Clues:

• Something supposedly lucky that's on the hoof?
• Waters garden bordering river in curved shape
• Last pair of gardeners in gardens attack the weeds? That’s a lucky thing
• Equine gardening equipment?
• Get lost, in a manner of speaking, after opening 12 across - some would say that's lucky
• One of those in stable environment going with loafer? Good luck with that!
• Most of those in 1 across get away we hear with lucky charm
• Gardening tool in a stable?
• Possible hack’s garden implement, a token of good luck
• Filly's standing by weed? That's lucky