Black-coated worker (10)
I believe the answer is:
undertaker
'worker' is the definition.
(undertaker is a kind of worker)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for undertaker that I've seen before include "Funeral director" , "One making promises" , "He'll deal with passing" , "One passing dangerously" .)