Boy who picks the winners? (5)
I believe the answer is:
ernie
This clue is a double definition.
'boy' is the first definition.
(boy's name)
'who picks the winners?' is the second definition.
(machine used in UK government bond scheme)
(Other definitions for ernie that I've seen before include "Computer selecting Premium Bond winners" , "Els, for example" , "Man - chooses Premium Bond winners" , "Eric's TV partner" , "Eric Morecambe & - - Wise" .)