Popular act? Certainly (6)

I believe the answer is:

indeed

'certainly' is the definition.
(thesaurus)

'popular act' is the wordplay.
'popular' becomes 'in'.
'act' becomes 'deed' (deed is a kind of act**).
'in'+'deed'='INDEED'

(Other definitions for indeed that I've seen before include "Unquestionably" , "Actually -- denied (anag)" , "beyond doubt" , "In reality" , "Without question" .)

I've seen this clue in The Guardian and The Telegraph.

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