What does the cryptic crossword clue "Crust should colour artisan bread first of all (4)" mean?

The definition is "Crust". The wordplay uses acrostic. first letters of "should colour artisan bread" = SCAB; definition: "Crust" The answer is SCAB.

Crust should colour artisan bread first of all (4)

Guardian Cryptic #29203 | 9 Across | 2023-10-17 flower