The word hairstreaks is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 17
Highest Scoring Words With Friends™ Plays In The Letters
Seven Letter Word Alert: (38 words)
arrests, artsier, ashiest, atresia, hastier, kaisers, karites, kashers, raisers, rashers, rashest, rasters, restirs, retasks, riskers, satires, searats, seastar, shakers, shakier, sharers, sharker, shirker, shitake, shrieks, shrikes, sierras, skaiths, skaters, starers, starker, streaks, striker, strikes, tarries, taskers, trasher, trashes