Victory sign under construction in old battle (6)

I believe the answer is:

verdun

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'old battle' is the definition.
'verdun' can be an answer for 'battle' (WW1 battle). I'm not certain of the 'old' bit.

'victory sign under construction in' is the wordplay.
'victory sign' becomes 'v' ().
'construction' is an anagram indicator (answer constructed from certain letters).
'in' is an insertion indicator.
'under' anagrammed gives 'erdun'.
'v' placed into 'erdun' is 'VERDUN'.

Can you help me to learn more?

(Another definition for verdun that I've seen is " Longest WW1 battle".)

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