24 across
Youngster
spends
year
on
benefit
(4)
Youngster spends year on benefit (4)
hints
0
checks
0
hints
The definition is at the end of the clue.
How the clue works
Look at benefit at the end — that's what you're after. You've got BOY (youngster), but you "spend" the Y (Y being the abbreviation for year), leaving you with BO, and then you stick ON on the end to get BOON.