What It Scores
XU is a valid word in the tournament list this site uses. Tile values only, before any premium square: 9 in Scrabble and 10 in Words With Friends. The letters break down as X8 U1.
Longer Words Containing XU
XU appears inside each of these, which is what makes it worth knowing as a hook.
Next: the Word Unscrambler for any letters at all, and the two and three letter lists. Full entry and definition at Merriam-Webster.