Second person supported by new agent and boyfriend (5,3)
I believe the answer is:
young man
'boyfriend' is the definition.
('young man' can be a synonym of 'boyfriend')
'second person supported by new agent' is the wordplay.
'second person' becomes 'you' (I've seen this before).
'supported by' says to put letters next to each other (letters go below - in down clue).
'new' becomes 'n'.
'agent' becomes 'gman' (G-man is an example).
'you'+'n'+'gman'='YOUNG MAN'
'and' is the link.
(Other definitions for young man that I've seen before include "Boyfriend - teenager" , "Old codger? Quite the opposite" , "sweetheart" , "Youth" .)