Crossword Genius

Dozenth couple requiring medical treatment (10)

Ross

I believe the answer is:

duodecimal

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'dozenth' is the definition.
Both the definition and answer are adjectives.
Maybe they are linked in a way I don't understand?

'couple requiring medical treatment' is the wordplay.
'couple' becomes 'duo' (synonyms).
'requiring' means one lot of letters go next to another.
'treatment' indicates an anagram (letters treated or processed differently).
'medical' is an anagram of 'decimal'.
'duo'+'decimal'='DUODECIMAL'

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I've seen this clue in The Times.
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