Crossword Genius

Score heroin after revealing a long list of others, in short (4)

Ross

I believe the answer is:

etch

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'score' is the definition.
(thesaurus)

I don't understand how the rest of the clue works.

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(Other definitions for etch that I've seen before include "What most engravers presumably find easy to do" , "Carve or engrave into surface" , "Cut using sharp instrument" , "Make picture by engraving metal" , "Make deep lines" .)

I've seen this clue in the Irish Times (Crosaire) and the Irish Times.
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