The war at sea started to hot up! (6)

I believe the answer is:

warmed

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'started to hot up' is the definition.
I can't judge whether this definition defines the answer.

'the war at sea' is the wordplay.
'at' says to put letters next to each other.
'sea' becomes 'med' (abbreviation of Mediterranean).
'war'+'med'='WARMED'

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(Other definitions for warmed that I've seen before include "gave enthusiasm" , "Heated" , "given thermal treatment" .)

I've seen this clue in the Evening Standard.

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