Crossword Genius

Commonplace affair, rotten deed (6-2-4)

Ross

I believe the answer is:

matter-of-fact

'commonplace' is the definition.
(thesaurus)

'affair rotten deed' is the wordplay.
'affair' becomes 'matter' ('matter' can be a synonym of 'affair'**).
'rotten' becomes 'off' (I've seen this before).
'deed' becomes 'act' (I've seen this before).
'matter'+'off'+'act'='MATTER-OF-FACT'

(Other definitions for matter-of-fact that I've seen before include "Down to earth" , "Commonplace" , "Straightforward and unemotional" , "Unemotional and practical" , "Unimaginative, emotionless" .)

I've seen this clue in The Telegraph.
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