Rogue sailor off on a quest (8)
I believe the answer is:
aberrant
'rogue' is the definition.
(I've seen this before)
'sailor off on a quest' is the wordplay.
I cannot really see how this works, but
'sailor' could be 'ab' (abbreviation for able seaman) and 'ab' is present in the answer.
'a' could be 'an' and 'an' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for aberrant that I've seen before include "Irregular" , "Transgressing" , "'Deviant, behaviour say (8)'" , "Deviating from the normal" , "Deviating from what is accepted" .)