Crossword Genius

A slim young man surprisingly showing generosity (13)

Ross

I believe the answer is:

magnanimously

'showing generosity' is the definition.

'a slim young man surprisingly' is the wordplay.
'surprisingly' indicates an anagram.
'a'+'slim'+'young'+'man'='aslimyoungman'
'aslimyoungman' is an anagram of 'MAGNANIMOUSLY'.

I've seen this clue in The Telegraph.
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