<html:select name="Category"
property="selectedCategoryDescription">
<html

ption value=""></html

ption>
<html

ptions name="Category"
property="categoryDescription"/>
</html:select>
Let me explain this:
--> drop down box/ combo box in
struts should be inside <html:select> or
in your case <s:select>
--> after selecting you have to save that selected value,
Here I am saving into Category's property/attribute
selectedCategoryDescription(I assumed it).
(Please customize it according to your need)
--> <html

ption value=""></html

ption> is where you keep default value
at the top
eg: <html

ption value="">--</html

ption>
eg: <html

ption value="">Select category Description</html

ption>
--> <html

ptions name="Category"
property="categoryDescription"/>
Here you are showing all the categoryDescription attribute of Category
Note: If you are using struts then hopefully you will be working with form beans. So customize this accordingly using form bean in your jsp page.
Hope this helps,
Abin