Center letter: i
Outer letter: n r t v a b
Answers (31):
  vibrant
  anti
  aria
  atria
  attain
  avian
  bait
  barbarian
  birria
  brain
  briar
  invariant
  irritant
  nirvana
  rabbi
  rabbit
  rain
  raita
  rani
  ribbit
  taint
  tannin
  tiara
  tibia
  tint
  titan
  train
  trait
  trivia
  vain
  variant