The word subtreasury 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™ Plays In The Letters subtreasury
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Seven Letter Word Alert: (22 words)
abusers, arbutus, arrests, auteurs, barters, basters, betrays, brayers, breasts, bureaus, bursars, bursary, bursate, busters, estuary, eustasy, rasters, reburst, starers, stayers, strayer, sutures