Spies sat about gathering in information (6)
I believe the answer is:
agents
'spies' is the definition.
(secret agents)
'sat about gathering in information' is the wordplay.
'about' is an anagram indicator.
'gathering' means one lot of letters goes inside another (gather can mean to acquire or bring in).
'in information' becomes 'gen' (I can't justify this - if you can you should believe this answer much more).
'sat' anagrammed gives 'ats'.
'ats' going around 'gen' is 'AGENTS'.
Can you help me to learn more?
(Other definitions for agents that I've seen before include "Sales reps" , "They operate on behalf of others" , "They act for others" , "Spies" , "travelling salesmen" .)