Scrape piece of rock to make screw (9)

I believe the answer is:

skinflint

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'make screw' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe there's an association between them I don't understand?

'scrape piece of rock' is the wordplay.
'scrape' becomes 'skin' (synonyms).
'piece of rock' becomes 'flint' (I can't justify this - if you can you should believe this answer much more).
'skin'+'flint'='SKINFLINT'

'to' acts as a link.

Can you help me to learn more?

(Other definitions for skinflint that I've seen before include "Niggard, scrooge" , "Very ungenerous or stingy person" , "A miserly person like Scrooge" , "A mean, miserly person" , "21 [MISER]" .)

I've seen this clue in The Independent.

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