The word grubstaking 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: 24
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (32 words)
abusing, airguns, arguing, barging, barking, basking, basting, braking, busking, busting, garbing, gastrin, grating, guitars, gusting, ratings, rusting, skating, staging, staking, staring, surging, tabuing, takings, tanukis, tasking, tubings, tugriks, turbans, tusking, unbaits, urgings