The representative is a guy (5)
I believe the answer is:
agent
'the representative' is the definition.
(agent is a kind of representative)
'a guy' is the wordplay.
'guy' becomes 'gent' (I've seen this in another clue).
'a'+'gent'='AGENT'
'is' is the link.
(Other definitions for agent that I've seen before include "Spy; representative" , "envoy" , "Representative - means" , "Middleman" , "One may be working" .)