Engraver using illegal aid in most of added material (9)

I believe the answer is:

inscriber

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'engraver' is the definition.
(I've seen this in another clue)

'in most of added material' is the wordplay.
'most of added material' becomes 'scriber' (I can't explain this - if you can you should believe this answer much more).
'in'+'scriber'='INSCRIBER'

'using illegal aid' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.

Can you help me to learn more?

(Another definition for inscriber that I've seen is " cutter is required".)

I've seen this clue in The Times.

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