One article not available in form of square - this food is usually round (5)

I believe the answer is:

pizza

'this food is usually round' is the definition.

I can't explain the remainder of the clue.

(Other definitions for pizza that I've seen before include "Italian food item" , "Margherita, Quattro Stagione or Marinara, perhaps?" , "round dish" , "Doughy dish" , "Dough-based dish" .)

I've seen this clue in The Independent.

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