Info gathered by heartless adjunct for spy (5)
I believe the answer is:
agent
'spy' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for agent that I've seen before include "factor in Scotland" , "Substance that exerts some force or effect" , "One's representative" , "Performer's manager" , "Spy; service provider" .)