Thorough removal of just over half of us by Thursday (2-5)

I believe the answer is:

in-depth

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

I don't understand the remainder of the clue.

(Other definitions for in-depth that I've seen before include "Thorough and intensive" , "Getting to the bottom of it" , "With thorough and extensive investigation" , "Full" , "Detailed and thorough" .)

I've seen this clue in The Independent.

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