Half warmed cold one? (3)

I believe the answer is:

war

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'cold one?' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.

'half warmed' is the wordplay.
'half' indicates taking half.
'warmed' with half the letters taken is 'WAR'.

Can you help me to learn more?

(Other definitions for war that I've seen before include "Armed hostility" , "Major conflict" , "Open hostility" , "Period of hostilities" , "Large-scale conflict" .)

I've seen this clue in the Evening Standard.

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