The word whiffletrees 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: 24
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (42 words)
eeriest, feelers, felsite, fertile, filters, fleeter, hefters, heftier, heifers, herself, lefties, lifters, refiles, reflies, reheels, reliefs, reshift, retiles, seether, sheeter, shelter, sheriff, shifter, slither, steelie, sterile, stiffer, stifler, sweeter, sweetie, swelter, swifter, trifles, wheeler, wheelie, whiffer, whiffet, whiffle, whistle, withers, wrestle, writhes