Priests start extending sermons (9)

I believe the answer is:

preaching

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'priests start extending sermons' is the definition.
I can't tell whether this definition defines the answer.

'priests start extending' is the wordplay.
'priests start' becomes 'p' (I can't explain this - if you can you should believe this answer much more).
'extending' becomes 'reaching' ('reach' can be a synonym of 'extend').
'p'+'reaching'='PREACHING'

Can you help me to learn more?

(Other definitions for preaching that I've seen before include "Delivering speech" , "Delivering a sermon" , "minister's job" .)

I've seen this clue in The Daily Express.

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