Crossword Genius

Old invader wanting ready rewards, fighting in this? (7,5,3)

Ross

I believe the answer is:

hundred years' war

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'this?' is the definition.
The definition suggests a singular noun which matches the answer.

'old invader wanting ready rewards fighting' is the wordplay.
'old invader' becomes 'hun' (I've seen this before).
'wanting' is a charade indicator (letters next to each other).
'fighting' is an anagram indicator (I've seen this in other clues).
'ready'+'rewards'='readyrewards'
'readyrewards' with letters rearranged gives 'dredyearswar'.
'hun'+'dredyearswar'='HUNDRED YEARS' WAR'

'in' acts as a link.

Can you help me to learn more?

I've seen this clue in The Guardian.
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