Hard to get one's teeth into side of cheese with mushy whey (5)

I believe the answer is:

chewy

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'hard' is the definition.
(thesaurus)

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

(Other definitions for chewy that I've seen before include "Requiring mastication, like toffee say" , "Tough to masticate" , "With a texture like toffee" , "Hard to eat" , "Soft and sticky (to eat)" .)

I've seen this clue in the Irish Times and the Irish Times (Crosaire).

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