Police caught lad misbehaving - a minor fault (10)
I believe the answer is:
'a minor fault' is the definition.
(I've seen this before)
'police caught lad misbehaving' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'misbehaving' indicates anagramming the letters.
'policeclad' with letters rearranged gives 'PECCADILLO'.
(Other definitions for peccadillo that I've seen before include "Trifling fault - I called cop (anag)" , "minor misdemeanour" , "Minor sin or fault" , "minor faux pas" , "A little wrong" .)