Perfect, best boy behind you, finally (7)
I believe the answer is:
utopian
'perfect' is the definition.
(associated in meaning)
'best boy behind you finally' is the wordplay.
'best' becomes 'top' (top can mean the very best).
'boy' becomes 'Ian' (man's name).
'behind' is a charade indicator (letters next to each other).
'you finally' becomes 'u' (I can't explain this - if you can you should believe this answer much more).
'top'+'ian'='topian'
'topian' put after 'u' is 'UTOPIAN'.
Can you help me to learn more?
(Other definitions for utopian that I've seen before include "Fantastic" , "Aspiring to impracticable perfection" , "Of supposed perfection" , "Just perfect, as in Thomas More's ideal country" , "Ideal; imaginary" .)