The word clingstone 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: 18
Highest Scoring Words With Friends™ Play In The Letters clingstone
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Seven Letter Word Alert: (29 words)
clients, cloning, closing, cognise, congest, consent, consign, costing, elogist, eloigns, glisten, gnostic, intones, lection, legions, lensing, lingoes, linnets, lionets, longest, nesting, notices, section, singlet, stencil, stoning, tensing, tension, tingles