Fit back four in place for Czechs (4)

I believe the answer is:

ague

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'fit' is the definition.
(ague is a fit of fever)

I can't explain the remainder of the clue.

(Other definitions for ague that I've seen before include "Sweating, shivering, fit (once)" , "Old word for fever" , "met with cheek in Twelfth Night" , "Fever (archaic)" , "Fever with shivers" .)

I've seen this clue in The Independent.

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