Agent (3)
'agent' is the definition.
(short for representative)
This is all the clue.
(Other definitions for rep that I've seen before include "Representative; fabric" , "Material for curtains" , "Fabric with a ribbed surface" , "Stuff" , "agent" .)
'agent' is the definition.
(spy is a kind of agent)
This is the entire clue.
(Other definitions for spy that I've seen before include "Enemy agent" , "Glimpse" , "Keep watch secretly, maybe for foreign government" , "Secret agent of government" , "One who collects secret information as for government" .)
'agent' is the definition.
(I know that proxy is a type of agent)
This is all the clue.
(Other definitions for proxy that I've seen before include "Delegated vote" , "Authorised agent" , "One voting on behalf of another" , "Person authorised to act on behalf of another" , "Authorised substitution" .)
'agent' is the definition.
(I know that agent can be written as broker)
This is all the clue.
(Other definitions for broker that I've seen before include "A dealer in stocks and shares" , "intermediary" , "Middleman, dealer" , "Negotiate with" , "One acts as an agent for others in buying and selling" .)