I'm with sympathy taking in boy's corruption (9)

I believe the answer is:

improbity

'corruption' is the definition.
(thesaurus)

'i'm with sympathy taking in boy's' is the wordplay.
'with' says to put letters next to each other.
'sympathy' becomes 'pity' (pity is a kind of sympathy).
'taking in' indicates putting letters inside.
'boy' becomes 'Rob' (boy's name).
'pity' enclosing 'rob' is 'probity'.
'im'+'probity'='IMPROBITY'

(Another definition for improbity that I've seen is " dishonesty".)

I've seen this clue in The Times.

Want a hint initially instead of a full solution? Install my app