Your clutch overheated due to the neoprene and metal discs rubbing together slightly while you held in the clutch. The neoprene (depending on old your bike is) plates are driven by your outer clutch basket that is driven off the crank. The metal plates are engaged by letting out the clutch and drive the inner clutch basket that is attached to the primary shaft of your transmission. This means that the outer clutch basket is always spinning when your engine is running.
Here is a diagram.
Outer clutch basket is number 1
Inner clutch basket is number 6
Neoprene clutch plates are number 11
Steel clutch plates are number 12
When you sat in traffic your neoprene and steel plates were rubbing together. They became very hot and possibly received damage as a result. The reduced friction from the heat allowed them to slip when you attempted to release the clutch in order to move forward.
When the clutch cooled the friction co-efficient went back up and you were able to engage the engine to the transmission via the clutch and be propelled forward.
Overheating your clutch is bad. It can warp your clutch discs (steel) or burn them up (neoprene). This can lead to future issues of clutch engagement. Overtime the situation can become worse and worse and aggravate itself until you need to replace both sets of neoprene and steel plates. This is not an outrageous cost if you are concerned.
You need to properly adjust your clutch. I'm assuming you have a cable adjustment on your handlebar
Adjusting a clutch cable on a motorcycle is an art form. You need to take your time and move the handlebars to the far right and left stops and check your adjustment each time. You want to have a little play in the lever. When you turn your handlebars far right on that model it WILL take up some of the play. You will need to adjust accordingly. When the handlebars are pointed straight there should be play in the clutch lever. It might seem a bit wonky but it's correct. Of course, you will want to keep the play to a minimum. Hence the art form. Find balance.
At the clutch cover Perhaps I should have put this above but what are doing is adjusting the clutch at the point where it joins your clutch cover with the adjustment and locking bolt. Be sure you have the second bolt to lock down the primary in order to keep your adjustment from changing. You will want to adjust here and at the handlebar. You want the clutch adjustment screw at the handlebar to be about halfway in the landing, you find the point by adjusting at the clutch cover, then you fine tune the adjustment up top.
You should have a big mess of graphite down here because you did such a great job of getting the liquid graphite into the cable. If you don't have a big mess, you did it wrong. Wash, rinse, repeat. You cannot have enough dry graphite in the cable housing.