Center letter: p
Outer letter: u d e l m n
Answers (56):
  pendulum
  deep
  deepen
  deepened
  depend
  depended
  dump
  dumped
  dupe
  duped
  duple
  epee
  lump
  lumped
  peddle
  peddled
  peed
  peel
  peeled
  peen
  peep
  peeped
  pend
  pended
  penmen
  penne
  penned
  peplum
  pepped
  pled
  plenum
  plum
  plume
  plumed
  plump
  plumped
  puddle
  puddled
  pule
  puled
  pull
  pulled
  pulp
  pulped
  pummel
  pummeled
  pump
  pumped
  punned
  umped
  unpeeled
  unpen
  unpenned
  upend
  upended
  upped