Agent's trade is page one outrage (9)

I believe the answer is:

espionage

I'm a little stuck... Click here to teach me more about this clue!

'agent's' is the definition.
(espionage agent is a kind of agent)

'trade is page one outrage' is the wordplay.
'is page one' can be anagrammed to 'ESPIONAGE'.
Though, I'm unsure how this is indicated.

Can you help me to learn more?

(Other definitions for espionage that I've seen before include "hush-hush work" , "seeking information" , "intelligence" , "undercover work" , "Practice of spying" .)

I've seen this clue in the Sydney Morning Herald.

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