A ninth op rectified short passage (8)

I believe the answer is:

antiphon

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'short passage' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe there's an association between them I don't understand?

'a ninth op rectified' is the wordplay.
'rectified' indicates an anagram.
'ninth'+'op'='ninthop'
'ninthop' anagrammed gives 'ntiphon'.
'a'+'ntiphon'='ANTIPHON'

Can you help me to learn more?

(Other definitions for antiphon that I've seen before include "Item sung in church" , "Short sentence" , "Type of church music" , "Church responsory" , "No hatpin, curiously, for the responsorial song" .)

I've seen this clue in The Times.

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