Take a sample maybe from Hampshire river (4)

I believe the answer is:

test

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'hampshire river' is the definition.
(River Test)

I don't understand the rest of the clue.

(Other definitions for test that I've seen before include "type of examination" , "Analyse" , "Examine to play international cricket match" , "Cricket match; exam" , "Trial - international game" .)

I've seen this clue in The Times.

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