Electronic expert conducting op in subtle surveillance (9)

I believe the answer is:

espionage

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'subtle surveillance' is the definition.
'espionage' can be an answer for 'surveillance' (thesaurus). I am not sure about the 'subtle' bit.

'electronic expert conducting op in' is the wordplay.
'electronic' becomes 'e' (as in e-mail or e-books).
'expert' becomes 'sage'.
'conducting op' becomes 'pion' (I can't justify this - if you can you should give a lot more credence to this answer).
'in' indicates putting letters inside.
'sage' enclosing 'pion' is 'spionage'.
'e'+'spionage'='ESPIONAGE'

Can you help me to learn more?

(Other definitions for espionage that I've seen before include "undercover work" , "007's game" , "seeking information" , "intelligence" , "agent's job" .)

I've seen this clue in The Hindu.

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