Hello apl76. Depending on which clock/weather widget you have, and which launcher (I'm assuming that you're running the stock launcher following the factory data reset) the procedure is a bit different: first, remove the whole thing by long pressing and dragging to the trash can. Then long press on an empty spot on the screen or hit menu > "add" and select widget. Then see if there are different versions of the clock widget, some with the weather and some not, some in different sizes, etc.

One type of clock app has a configuration menu that you get to via an icon in the app drawer.

 

Long press on screen then choose widget then browse all HTC widgets. Scroll through and you will find lots of clocks. The one after the weather clock is the social clock. The removes the weather and replaces it with feeds to social sites like twitter etc. That is your only other option if you are using HTC widgets. AFAIK you can't remove the weather from the HTC widget.

There are widgets from other suppliers out there - look in the market to find them.