What It Scores
ST is a valid word in the tournament list this site uses. Tile values only, before any premium square: 2 in Scrabble, 2 in Words With Friends, 2 in Wordfeud. The letters break down as S1 T1.
Longer Words Containing ST
ST 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.