Well groomed singletrack. Fast and fun when it's dry. If the ground is wet you might want to think about going to another place.
The best thing to do is to get a copy of the White Clay Creek map and fill in the trails at the Trailhead Map for Middle Run.
The Lenape Trail makes a loop around the entire natural area and is a pretty fun loop. Try Following this or just get lost and rip around until you pop back out at the Parking area.
I'll try to explain a decent loop, but it's best to figure it out on your own.
At the trailhead map you will see singletrack to your right thru the field. Take this into the woods and follow it staying to your right until you get to a bridge that crosses Middle Run. After you cross the bridge you will pass a fallen tree that has been flattened on top so you can ride across it. Hang to your left and climb the trail to the top of the hill. Hang right and follow the Double track size trail down around the green water tower. This connects to the Snow Goose trail which consists of 3 spurs all connecting together. I usually hang left and follow it down to the creek and head right along the creek all the way back to the bridge. Cross back over the bridge and follow the way you came staying to the Right as trails split off to the left. This is now the Tri Valley Trail/Lenape Trail. Follow this across Fox Den Road and past Deacon's Walk Spur. You will come to an intersection of two trails. Going straight will pop you out in a development and onto Smith Mill Road. Follow this straight across Paper Mill Road to White Clay Creek State Park. Or to stay in Middle Run hang a Left up thru the field. This is a continuation of the Lenape Trail. Follow it back across Fox Den Road and stay on the Lenape Trail, there are small signs. You will come out on a Dirt road at the turn in to were you parked. Go straight across the road and get onto Double Horseshoe Trail, follow this across Possom Hollow Road down into the woods on the otherside. You can really rip thru here. Keep on the main trail it will meet back up with Lenape Trail. Take the Chapel Hill spur around. At the 3 way intersection hand Left back down into the woods. You will pop out back down at Middle Run across from the Snow Goose trail. Here you can either cross the creek on the stepping stone and follow it back or hang a left back up over the hill on Possum Hollow Trail and head right back to the trail head.
This is a good place to get lost and there is no doubt my trail directions are lacking a bit. There are new trails that are not on the maps so it's easy to head the wrong way. So follow these directions loosely and have fun.