I have successfully defended it 2x in ranked 10xx, both the same way.
I sneak _some_ villagers out onto the side of the maps and the back bases.
They make more TCs and also a siege workshop.
Gather some light cav and break into their base and harass their eco. Build a castle on their face. Eventually they realize they need to bring their army home. Use light cav to snipe any organ guns that are alone.
Build another castle or siege workshop to take out the castle in your base. Never fight their army always just avoid it and keep growing your eco and eventually crush their army with Cav.