Mark, a seaman, once held sacred (6)
I believe the answer is:
scarab
'once held sacred' is the definition.
I can't tell whether this defines the answer.
'mark a seaman' is the wordplay.
'mark' becomes 'scar' (mark left by an injury).
'a seaman' becomes 'ab' (short for able seaman).
'scar'+'ab'='SCARAB'
Can you help me to learn more?
(Other definitions for scarab that I've seen before include "Sacred Eygptian beetle" , "Beetle, sacred to the ancient Egyptians" , "Beetle, considered to be divine in ancient Egypt" , "Beetle considered divine by ancient Egyptians" , "Dung beetle - ancient Egyptian cut gem" .)