The word clattering 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: (48 words)
aligner, angelic, article, carting, cattier, catting, central, certain, citrate, cittern, clatter, clinger, clitter, crating, elating, gelatin, genital, glacier, glancer, glitter, gracile, granite, ingrate, latrine, lattice, learing, letting, nattier, nictate, nitrate, ratline, ratting, realign, recital, reclang, reliant, retinal, ringlet, tactile, tagline, tangier, tantric, tearing, tertial, tetanic, tingler, tracing, trenail