Crossword Genius

Bill’s solution penetrates synthetic materials (10)

Ross

I believe the answer is:

polyesters

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'synthetic materials' is the definition.
'polyesters' can be an answer for 'materials' (polyester is a kind of material). I am not certain of the 'synthetic' bit.

'bill's solution penetrates' is the wordplay.
'bill's' becomes 'posters' ('poster' can be a synonym of 'bill').
'solution' becomes 'lye' (I've seen this before).
'penetrates' indicates putting letters inside.
'posters' placed around 'lye' is 'POLYESTERS'.

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I've seen this clue in The Times.
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