首事

shǒushì
  1. (archaic) the most pressing matter
  2. the most pressing matter

Wiktionary

Entry Composition

1 首 shǒu
  1. head
  2. chief
  3. first (occasion, thing etc)
  4. classifier for poems, songs etc
=2 事 shì
  1. matter
  2. thing
  3. item
  4. work
  5. affair

classifiers: 件, 樁, 回
=2 事 zì
  1. alternative form of 倳 (zì, “to establish”)
  2. alternative form of 剚 (zì, “to stab”)