A tinker spattered substance in hair (7)

I believe the answer is:

keratin

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'substance in hair' is the definition.
'keratin' can be an answer for 'substance' (keratin is a kind of substance). I'm not sure about the 'in hair' bit.

'a tinker spattered' is the wordplay.
'spattered' indicates an anagram.
'a'+'tinker'='atinker'
'atinker' with letters rearranged gives 'KERATIN'.

Can you help me to learn more?

(Other definitions for keratin that I've seen before include "Constituent of hair/nails" , "Rate ink (anag) - fibrous protein" , "Protein found in hair and nails" , "Material in hooves and nails" , "Hair, nails substance" .)

I've seen this clue in The Guardian.

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