Create an action of the type "Format Tag field" e.g. for TITLE with a format string that looks like this:
$left(%title%,$strstr(%title%,' www'))
(note the blank in front of www)
Create a similar action for the field Artist
The idea is to let MP3tag search for " www" inside the string, determine the position of that string and trim the field up to that position.
As this function return zero if the " www" is not found you will end up with an empty string if there is no " www" in it, so filter your list first before you start the action.