A field in the Middle Ages (3)

I believe the answer is:

lea

'a field' is the definition.
(lea can mean a meadow or field of grass)

'in the middle ages' is the wordplay.
'in' indicates the answer is hidden within the clue.
'LEA' is hidden in the letters of 'middle ages'.

(Other definitions for lea that I've seen before include "pastoral setting" , "Open country" , "Tract of pastureland" , "Land growing grass" , "Grass area" .)

I've seen this clue in The Globe and Mail.

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