Center letter: r
Outer letter: g n o p u w
Answers (23):
  grownup
  gorgon
  gorp
  grog
  group
  grow
  grown
  guru
  poor
  porn
  porno
  pour
  prong
  pronoun
  prop
  prow
  purr
  rung
  ungroup
  unworn
  worn
  wrong
  wrung