What does the cryptic crossword clue "Hard-working souls due to be replaced (8)" mean?

The definition is "Hard-working". The wordplay uses an anagram. anagram of SOULS + DUE = SEDULOUS; definition: "Hard-working" The answer is SEDULOUS.

Hard-working souls due to be replaced (8)

Daily Mail Cryptic #16874 | 1 Across | 2022-07-06 flower