Crossword Genius

Black and sticky but I've heard a second helping goes well with fish. (3)

Ross

I believe the answer is:

tar

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'black' is the definition.
(I've seen this in other clues)

I can't explain the remainder of the clue.

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(Other definitions for tar that I've seen before include "Sticky substance used in road construction" , "Informal sailor, the rat" , "Product of coal" , "Black substance in cigarettes" , "Crewman" .)

I've seen this clue in The Irish Times.
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