Aid to a certain diagnosis -- inaction seems out of order (13)

I believe the answer is:

amniocentesis

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'aid to a certain diagnosis' is the definition.
I can't judge whether this defines the answer.

'inaction seems out of order' is the wordplay.
'out of order' indicates an anagram.
'inaction'+'seems'='inactionseems'
'inactionseems' is an anagram of 'AMNIOCENTESIS'.

Can you help me to learn more?

(Other definitions for amniocentesis that I've seen before include "Technique for screening unborn children" , "test" .)

I've seen this clue in The Telegraph.

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