The word straitens 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: 10
Highest Scoring Words With Friends™ Play In The Letters straitens
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Seven Letter Word Alert: (33 words)
antsier, artiest, artists, attires, inserts, instars, instate, iratest, nastier, natters, nattier, nitrate, restain, retains, retinas, retints, satires, seitans, sestina, sinters, sitters, stainer, staters, statins, strains, straint, straits, striate, tasters, tastier, tinters, transit, tsarist