Crossword Genius

Smart piece of kit uses down link (7)

Ross

I believe the answer is:

necktie

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'smart piece of kit' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

'down link' is the wordplay.
'down' becomes 'neck' (both can mean to finish a drink).
'link' becomes 'tie' (synonyms).
'neck'+'tie'='NECKTIE'

'uses' acts as a link.

Can you help me to learn more?

(Other definitions for necktie that I've seen before include "American garment" , "Ascot?" , "Male dress item (US)" , "one may get collared!" , "one can get knotted" .)

I've seen this clue in The Independent.
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