The word underparts 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
Seven Letter Word Alert: (61 words)
asunder, darners, darters, departs, drapers, dustpan, entraps, errands, errants, natured, natures, panders, panters, parents, partner, pasture, peanuts, pedants, petards, praters, pretans, prudent, pruners, punster, punters, ranters, rapture, restrap, retards, retraps, returns, saunter, sparred, spurned, spurner, spurred, spurted, spurter, stander, standup, starred, suntrap, traders, trepans, tundras, turners, undrape, undrest, unparse, unrated, unsated, unstrap, untaped, untraps, untread, updater, updates, uprated, uprates, uprears, uptrend