I'd connect somehow with another one falling at the same time (10)

I believe the answer is:

coincident

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'at the same time' is the definition.
(synonyms)

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

(Other definitions for coincident that I've seen before include "Matching" , "Occurring together" , "in the same place" .)

I've seen this clue in The Guardian.

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