RIDDER is a playable word

ridder Scrabble® Dictionary

noun
pl. ridders
one that rids
23 Playable Words can be made from "RIDDER"
   2-Letter Words (5 found)
   3-Letter Words (7 found)
   4-Letter Words (5 found)
   5-Letter Words (5 found)
   6-Letter Words (1 found)