心腹大患

xīnfùdàhuàn

serious hidden trouble or danger

Wiktionary

Entry Composition

1 心腹 xīnfù trusted aide; confidant
=2 大 dà
  1. big; large; great
  2. older (than another person)
  3. eldest (as in 大姐 dàjiě)
  4. greatly; freely; fully
  5. (dialect) father
  6. (dialect) uncle (father's brother)
=2 大 dài see 大夫 dàifu
3 患 huàn
  1. to suffer (from illness)
  2. to contract (a disease)
  3. misfortune
  4. trouble
  5. danger
  6. worry