One adept at spying and at taking in information (5)
I believe the answer is:
agent
'one adept at spying' is the definition.
(secret agent)
'at taking in information' is the wordplay.
'taking in' means one lot of letters goes inside another.
'information' becomes 'gen' (gen can informally mean information).
'at' going around 'gen' is 'AGENT'.
'and' acts as a link.
(Other definitions for agent that I've seen before include "Delegate" , "One does business on behalf of another" , "Actors' manager" , "factor in Scotland" , "Person who does business on behalf of another" .)