You dictated right extension for original document (6)
I believe the answer is:
urtext
'original document' is the definition.
The definition suggests a singular noun which matches the answer.
'you dictated right extension' is the wordplay.
'dictated' shows a homophone (sound like) (how it might sound if someone dictated it).
'right' becomes 'rt' (abbreviation as in Rt Hon- the Right Honourable).
'extension' becomes 'ext' (abbreviation, as in a telephone extension).
'you' is a homophone of 'u'.
'u'+'rt'+'ext'='URTEXT'
'for' acts as a link.
Can you help me to learn more?
(Another definition for urtext that I've seen is " The earliest version of a piece of writing".)