Fever that's non-specific having five going down (4)

I believe the answer is:

ague

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'fever' is the definition.
(I've seen this in another clue)

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

(Other definitions for ague that I've seen before include "Malarial fever; chill" , "met with cheek in Twelfth Night" , "Fever with shivers" , "attack" , "Malaria, for example" .)

I've seen this clue in The Times.

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