Working daily, in theory (2,5)

I believe the answer is:

on paper

'in theory' is the definition.
('on paper' can be a synonym of 'in theory')

'working daily' is the wordplay.
'working' becomes 'on'.
'daily' becomes 'paper' (newspaper).
'on'+'paper'='ON PAPER'

(Other definitions for on paper that I've seen before include "Theoretical" , "Planned (in theory)" , "Where one might write" , "In writing" , "Hypothetically" .)

I've seen this clue in The Telegraph.

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