Detective scrubs face for evening speech (9)

I believe the answer is:

discourse

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'speech' is the definition.
(discourse is a kind of speech)

'detective scrubs face for evening' is the wordplay.
'detective' becomes 'di' (Detective Inspector abbreviation).
'face' suggests taking the first letters.
'for evening' becomes 'course' (I can't explain this - if you can you should give a lot more credence to this answer).
The first letter of 'scrubs' is 's'.
'di'+'s'+'course'='DISCOURSE'

Can you help me to learn more?

(Other definitions for discourse that I've seen before include "(Formal) talk" , "verbal communication" , "Formal discussion of a topic" , "To hold a conversation" , "Communication verbally" .)

I've seen this clue in The Independent.

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