Auditor set out on board ship (8)
I believe the answer is:
listener
'auditor' is the definition.
('listener' can be a synonym of 'auditor')
'set out on board ship' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'on board' means one lot of letters goes inside another.
'ship' becomes 'liner' (liner is a kind of ship).
'set' with letters rearranged gives 'ste'.
'ste' going inside 'liner' is 'LISTENER'.
(Other definitions for listener that I've seen before include "Person paying aural attention" , "Former BBC magazine" , "One who hears" , "Auditor" , "Radio adherent" .)