Crossword Genius

Youngster with a large sum (5)

Ross

I believe the answer is:

total

'sum' is the definition.
('total' can be a synonym of 'sum')

'youngster with a large' is the wordplay.
'youngster' becomes 'tot' (tot is a kind of youngster**).
'with' means one lot of letters go next to another.
'large' becomes 'l'.
'tot'+'a'+'l'='TOTAL'

(Other definitions for total that I've seen before include "French oil and gas company" , "final answer" , "Sum, aggregation" , "Unqualified" , "Complete, entire amount" .)

I've seen this clue in The Telegraph.
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