The word demisters 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: 13
Highest Scoring Words With Friends™ Play In The Letters demisters
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Seven Letter Word Alert: (24 words)
demerit, demises, demists, deserts, desires, dessert, diester, dieters, dimeter, merited, messier, metrise, misters, mitered, reedits, reemits, resides, restems, retimed, retimes, smiters, strides, tressed, tridems