If wearing regular clothes is something that works for you and your chain is exposed, there are several options for keeping your pants out of the chain. Use a band or clip, roll them up or worst case tuck them into your socks. My commute used to be multi-modal. A short ride to the station, then 15 to 20 minutes on the train and then another short ride to the office. I wore regular clothes and don't recall keeping my pants clean being much of a problem.

In the winter I'd wear long underwear under the pants and on really cold days I'd wear ski pants over the top. It was fine for short trips.

Now my commute is 6 miles each way and I use it for exercise. I get sweaty so I change. Even if I was just taking my sweet time though, winter is a different beast. It gets very cold here and there are many days that you really need some winter gear if you're going to spend any significant amount of time outdoors. Office clothing is going to cut it, even if it's wool.

PaulRivers mentioned Novara Headwind pants. They're not quite tights but have a snugger fit so no chain worries. I actually use them most of the winter but I wear tights underneath them. A good pair of long underwear might do the job instead of the tights underneath if you wanted.

When it gets below zero I bring out the big guns, - the Pearl Izumi Amfibs. I wear those over tights too.

I didn't get the OP's location so I'm not sure how cold it gets where they live but what I wear during the Fall are running pants. They're not tights but they have a close fit. You can wear regular underwear or long underwear underneath them. Mine are made by Ronhill and are super comfortable. They're fine down into the 40's, maybe mid 30's with something underneath. The wind will go right through them though.