In general, it's a very bad idea to remove or rename a field -- if you are not positive that it's one you added yourself, do not change it because it may be used for something. To remove something you do not want to use, you should simply edit it out of your templates.

If it's a listing field in WSN 9.0+, you can edit or remove it via Admin Panel -> Listings -> Listing Fields. Otherwise, if you're absolutely certain that the field isn't being used anywhere, you can remove it through Admin Panel -> Customizations -> Add Fields by clicking the "Show/hide advanced options" link. Note that removing a field via the add fields page (unlike the Listing Fields page) may not remove all of the associated HTML from your templates unless the code is nearly unchanged from the default... you may thus have to manually edit your templates to remove stuff.

If you rename a field, be certain that you edit all templates to use the new name of the field and the new template variable for it. You may wish to use the Admin Panel -> Miscellaneous -> Advanced Options page to do a bulk replace of all instances of the old field name and template variable in all templates with the new name and template variable of the field. In doing this be sure to replace both the field itself and the associated template variable -- in you rename field1 to field2, you must mass-replace field1 with field2 AND mass replace {LINKFIELD1} with {LINKFIELD2}.