Fish sauce from sailor doubled energy (7)
I believe the answer is:
tartare
'fish sauce' is the definition.
(I've seen this before)
'sailor doubled energy' is the wordplay.
'sailor' becomes 'tar' (slang term for a sailor).
'doubled' says to double the letters.
'energy' becomes 'e' (physics symbol as in E=mc2).
'tar' duplicated is 'tartar'.
'tartar'+'e'='TARTARE'
'from' acts as a link.
(Other definitions for tartare that I've seen before include "Mayonnaise dressing served with fish" , "(Mayonnaise) sauce; raw (steak)" , "(Of fish or beef) served chopped and raw in small cakes" , "Mayonnaise-based sauce with capers, eaten with fish" , "Saucy thing" .)