The word leatherneck 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: 22
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (32 words)
archlet, central, chanter, cheater, chelate, cleaner, earthen, enteral, enthral, eternal, hearken, hearten, heckler, hectare, kneeler, leacher, leather, lectern, leecher, rechalk, recheat, reclean, reelect, reenact, retaken, reteach, rethank, tackler, teacher, thanker, tranche, treacle