Boy with flat on street (6)
I believe the answer is:
steven
'boy' is the definition.
'flat on street' is the wordplay.
'flat' becomes 'even' (level).
'on' is a charade indicator (letters next to each other).
'street' becomes 'st' (abbreviation).
'even' put after 'st' is 'STEVEN'.
'with' is the link.
(Other definitions for steven that I've seen before include "voice" , "- Spielberg, US director" , "Man" .)