Crossword Genius

Insignificant person to enforce delay upon being picked up (10)

Ross

I believe the answer is:

makeweight

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'insignificant person' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for makeweight that I've seen before include "It helps the balance" , "Unimportant addition to complete something" , "deficiency" , "An unimportant extra" , "Filler" .)

I've seen this clue in The Times.
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