Large plain stable dam (4)

I believe the answer is:

mare

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This might be a double definition.

'large plain' is the first definition.
'mare' can be an answer for 'plain' (thesaurus). I'm unsure of the 'large' bit.

'stable dam' is the second definition.
'mare' can be an answer for 'dam' (I've seen this in another clue). I'm not sure about the 'stable' bit.

Can you help me to learn more?

(Other definitions for mare that I've seen before include "Adult female horse" , "Ream (anag)" , "Horse; lunar sea" , "For classicists, sea" , "Female quadruped" .)

I've seen this clue in The Guardian.

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