Crust should colour artisan bread first of all (4)
I believe the answer is:
scab
'crust' is the definition.
(I've seen this in another clue)
'should colour artisan bread first of all' is the wordplay.
'first of all' suggests taking the first letters.
The initial letters of 'should colour artisan bread' is 'SCAB'.
(Other definitions for scab that I've seen before include "Someone who works during a strike" , "sign of wound healing" , "Strike-breaker; skin disease in animals" , "part of healing process" , "Crust-like surface over a wound" .)