Evil immoral sailor (6)
I believe the answer is:
sinbad
'sailor' is the definition.
(I've seen this before)
'evil immoral' is the wordplay.
'evil' becomes 'sin' (I've seen this before).
'immoral' becomes 'bad' ('bad' can be a synonym of 'immoral').
'sin'+'bad'='SINBAD'
(Other definitions for sinbad that I've seen before include "Legendary mariner noted for seven voyages" , "Legendary sailor from Arabian nights" , "Adventurous sailor of Arabian Nights or pantomime" , "Literary sailor" , "Arabian Nights sailor who made seven voyages" .)