Happy to find the boy after good start (4)
I believe the answer is:
glad
'happy' is the definition.
(I know that happy can be written as glad)
'the boy after good start' is the wordplay.
'the boy' becomes 'lad' (informal term for boy).
'after' is a charade indicator (letters next to each other).
'start' suggests taking the first letters.
The initial letter of 'good' is 'g'.
'lad' put after 'g' is 'GLAD'.
'to find' is the link.
(Other definitions for glad that I've seen before include "part of Iris's family" , "Happy, pleased" , "Feeling pleasure" , "Joyful" , "bright?" .)