Cistern with lid off was minging (4)

I believe the answer is:

tank

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'cistern' is the definition.
(thesaurus)

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

(Other definitions for tank that I've seen before include "Miltary vehicle" , "Military machine" , "Military vehicle - fuel container" , "Cistern - armoured vehicle" , "Car fuel container" .)

I've seen this clue in The Independent.

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