You can use this step in a script:
Set Field [Notes::Note; Substitute ( Lower ( Notes::Note ) ; "extraneous " ; "" )]
NB: 1. Replace Notes::Note with your tablename::fieldname
2. The substitute function is case sensitive so the Lower function controls for that.
3. Replace "extraneous" with the word you are trying to get rid of. Include a space after the word (inside the inverted commas) and your remaining text won't end up with two spaces between words.