Yes, duns is a Scrabble word!
...and is worth 5 points in Scrabble, and 7 points in Words with Friends
duns
Verb
1. Treat cruelly
2. Persistently ask for overdue payment
3. Cure by salting
4. Make a dun color
Noun
1. Horse of a dull brownish grey color
2. A color or pigment varying around a light grey-brown color
What Scrabble words can I make with the letters in duns?
3 Letter Words
2 Letter Words