A win for little boy Blue (7)
I believe the answer is:
victory
'a win' is the definition.
(a win is a victory)
'little boy blue' is the wordplay.
'little boy' becomes 'vic' (short for Victor).
'blue' becomes 'tory' (I've seen this before).
'vic'+'tory'='VICTORY'
'for' is the link.
(Other definitions for victory that I've seen before include "Success against an opponent" , "Triumph" , "Successful ending to a struggle or contest" , "Success in a contest" , "ship" .)