The word threaders 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: 12
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (39 words)
adherer, adheres, darters, dearest, dearths, earthed, hardest, hatreds, headers, headset, hearers, hearsed, hearted, heaters, herders, readers, reasted, redates, reheard, rehears, reheats, rereads, reshare, retards, retears, retrade, retread, sedater, serrate, sheared, shearer, starred, tasered, tearers, threads, traders, trashed, trasher, treader