The word deferential 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™ Play In The Letters
Seven Letter Word Alert: (55 words)
alerted, altered, arenite, deerlet, defiant, defiler, definer, deflate, deleter, detrain, dilater, draftee, enteral, entered, eternal, fainted, fainter, federal, fertile, fielder, fileted, fireant, fleeted, fleeter, flirted, indraft, inflate, latrine, leafier, learned, lenited, lineate, needier, needler, ratline, redealt, redline, refiled, refined, reflate, related, reliant, relined, retiled, retinal, teenier, tendril, tradein, trailed, trained, trainee, treadle, trenail, triaene, trifled