Sailors having starter of eel, served raw (7)
I believe the answer is:
tartare
'served raw' is the definition.
(term in cuisine meaning served raw)
I don't understand the remainder of the clue.
(Other definitions for tartare that I've seen before include "(Of fish or beef) served chopped and raw in small cakes" , "(Mayonnaise) sauce; raw (steak)" , "Type of mayonnaise sauce" , "Saucy thing" , "9, 7" .)