Crossword Genius

Double volume in hurry to become a thousand (9)

Ross

I believe the answer is:

lookalike

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'double' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for lookalike that I've seen before include "Copy" , "Double" , "twin?" , "Doppelganger" .)

I've seen this clue in The Times.
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