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For medics, filter calls about unknown drug (7)

Ross

I believe the answer is:

dialyse

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'for medics filter' is the definition.
I can't judge whether this defines the answer.

'calls about unknown drug' is the wordplay.
'calls' becomes 'dials' (I've seen this in another clue).
'about' indicates putting letters inside.
'unknown' becomes 'y' (algebra).
'drug' becomes 'e' (E is another name for ecstasy).
'dials' going around 'y' is 'dialys'.
'dialys'+'e'='DIALYSE'

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