Yes, duty is a Scrabble word!
...and is worth 8 points in Scrabble, and 8 points in Words with Friends
duty
Noun
1. The social force that binds you to the courses of action demanded by that force; every opportunity, an obligation; every possession, a duty"- John D.Rockefeller Jr
2. Work that you are obliged to perform for moral or legal reasons
3. A government tax on imports or exports
What Scrabble words can I make with the letters in duty?
2 Letter Words