One who holds back concerning sieve (10)

I believe the answer is:

restrainer

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'one who holds back' is the definition.
The definition suggests a singular noun which matches the answer.

'concerning sieve' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'sieve' becomes 'strainer' (I've seen this before).
're'+'strainer'='RESTRAINER'

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I've seen this clue in The Daily Express.

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