Center letter: c
Outer letter: e k m o a b
Answers (30):
  comeback
  aback
  acme
  back
  backcomb
  became
  beck
  become
  bocce
  bock
  cacao
  cake
  came
  cameo
  camo
  coca
  cock
  cocoa
  coke
  coma
  comb
  combo
  come
  comma
  cook
  cookbook
  emcee
  mace
  mecca
  mock