Old legal right in French is superior (7)

I believe the answer is:

estover

'old legal right' is the definition.
(historical legal term)

'french is superior' is the wordplay.
'french is' becomes 'est' ('is' in French).
'superior' becomes 'over' (I've seen this in other clues).
'est'+'over'='ESTOVER'

'in' is the link.

(Another definition for estover that I've seen is " Legal right".)

I've seen this clue in The Guardian.

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