Center letter: n
Outer letter: a d j o r u
Answers (22):
  adjourn
  adorn
  anon
  around
  darn
  donor
  dunno
  journo
  naan
  nada
  nana
  noon
  noun
  radon
  rand
  rando
  roan
  rondo
  round
  runaround
  udon
  undo