The word streetlight 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: 16
Highest Scoring Words With Friends™ Play In The Letters streetlight
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Seven Letter Word Alert: (31 words)
eighter, elegist, elegits, glister, glitter, gristle, hitters, letters, lighter, litters, relight, resight, retiles, retilts, retitle, settler, shelter, sighter, sleight, slither, slitter, sterile, stilter, testier, tethers, thistle, tighter, tilters, tithers, titters, trestle