Drug [possessive-の] secret-selling [topic-は] root-and-all exterminate must.
根こそぎ ('root and all, completely') is an adverb for total removal — 根 ('root') + こそぎ (scraping). 絶やす ('to exterminate, to wipe out') is the transitive form of 絶える. 密売 ('secret selling/trafficking') — 密 ('secret') + 売 ('sell').