No arch ferryman (6)
I believe the answer is:
charon
'ferryman' is the definition.
(ferryman of Hades in Greek myth)
'no arch' is the wordplay.
'no arch' anagrams to 'CHARON'.
But, I'm unsure how the anagram is indicated.
Can you help me to learn more?
(Other definitions for charon that I've seen before include "Boatman across the river Styx" , "He ferries dead over Styx" , "Ferryman who brought the souls of the dead across the river Styx" , "Hell's mythical boatman" , "Ferryman on river of Hades" .)