Yes, duet is a Scrabble word!
...and is worth 5 points in Scrabble, and 6 points in Words with Friends
duet
Noun
1. Two items of the same kind
2. Two performers or singers who perform together
3. A pair who associate with one another
4. A musical composition for two performers
5. (ballet) a dance for two people (usually a ballerina and a danseur noble)
What Scrabble words can I make with the letters in duet?
3 Letter Words
2 Letter Words