Center letter: u
Outer letter: d g h n o r
Answers (23):
  groundhog
  dough
  dour
  drug
  dugong
  dung
  dunno
  gourd
  ground
  guru
  hound
  hour
  hung
  noun
  nunhood
  rough
  round
  rung
  udon
  undo
  unground
  unhood
  unhung