Page one is encrypted in secret work (9)
I believe the answer is:
espionage
'secret work' is the definition.
(the work of a spy)
'page one is encrypted' is the wordplay.
'encrypted' indicates an anagram.
'page'+'one'+'is'='pageoneis'
'pageoneis' anagrammed gives 'ESPIONAGE'.
'in' is the link.
(Other definitions for espionage that I've seen before include "seeking information" , "agent's job" , "007's game" , "undercover work" , "Practice of spying" .)