Specious excuse to start preaching on a written subject (7)

I believe the answer is:

pretext

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'specious excuse' is the definition.
(I've seen this before)

'start preaching on a written subject' is the wordplay.
'start' indicates taking the first letters.
'on' becomes 're' (regarding).
'a written subject' becomes 'text' (I've seen this in another clue. I am not sure about the 'written' bit.).
The initial letter of 'preaching' is 'p'.
'p'+'re'+'text'='PRETEXT'

'to' acts as a link.

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(Other definitions for pretext that I've seen before include "Insincere excuse" , "Fictitious excuse" , "Reason put forward to conceal the true one" , "False reason as justification for an action" , "False reason, guise" .)

I've seen this clue in the Evening Standard.

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