Want half of mine to go to the boy (4)
I believe the answer is:
need
'want' is the definition.
(synonyms)
'half of mine to go to the boy' is the wordplay.
'half of' suggests halving the letters.
'to go to' means one lot of letters go next to another.
'the boy' becomes 'ed' (short for Edward).
'mine' cut in half is 'ne'.
'ne'+'ed'='NEED'
(Other definitions for need that I've seen before include "state requiring relief" , "A condition" , "Necessity" , "''A friend in .... is a friend indeed''" , "What's lacking" .)