Stuff youngster carries round (4)
I believe the answer is:
load
'stuff' is the definition.
(load is a kind of stuff)
'youngster carries round' is the wordplay.
'youngster' becomes 'lad' (I've seen this before).
'carries' means one lot of letters goes inside another.
'round' becomes 'o' (round can mean a round object).
'lad' enclosing 'o' is 'LOAD'.
(Other definitions for load that I've seen before include "that's put on commercial vehicle" , "Weigh down" , "Weight, source of pressure" , "Goods carried by a large vehicle" , "pack" .)