The First Clerk is the trusted chief financial advisor to the Ferengi Grand Nagus.
It is not uncommon for these officials to be assassinated with the Nagus should there be a catastrophic profit loss that affects the Ferengi Alliance. (DS9 episode: "Ferengi Love Songs")
Quark was briefly First Clerk in 2373. Krax is Rom's First Clerk. (DS9 episode: "Ferengi Love Songs", DS9 novel: Ferenginar: Satisfaction is Not Guaranteed)