Plant found in the middle of resown barren fields (6)

I believe the answer is:

sorrel

'plant' is the definition.
(sorrel is a kind of plant)

I can't explain the rest of the clue.

(Other definitions for sorrel that I've seen before include "Light brown: salad leaf" , "Reddish brown horse or sharp-tasting herb" , "Light-chestnut horse" , "Edible plant of the dock family" , "Sour-tasting leaves used in salads and sauces" .)

I've seen this clue in The Guardian.

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