It helps edit work of sad writer (4,6)

I believe the answer is:

blue pencil

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'it helps edit work' is the definition.
I know nothing about this answer so I cannot tell whether this works.

'sad writer' is the wordplay.
'sad' becomes 'blue' (similar in meaning).
'writer' becomes 'pencil' (something which writes).
'blue'+'pencil'='BLUE-PENCIL'

'of' acts as a link.

Can you help me to learn more?

(Other definitions for blue pencil that I've seen before include "Censor" , "Edit" , "Censor's implement" .)

I've seen this clue in The Irish Times.

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